rpenmanparker 

It is such a personal thing.

It is a lot different when you have more than one bike. Some you want to be fully up to date, others not so much. I have had three bikes at all times since 1990. Two bikes between 1986 and 1990. One before that. The second bike was on a Trek glued Aluminum frame and was 126 mm OLD in the rear. When it was obvious that wasn't going to be sufficient for wider cassettes and OLD wheels going forward, and it couldn't be cold set, it was time to get rid of it. I don't want any of my bikes to become antiques and surely not to limit my ability to fully modernize them. Even though they may not all be right up to the minute, I am not interested in preserving the past. So to me it becomes obvious when it is time to call it quits with a bike. When I decided to never again travel with a bike, it was obviously time to ditch my Romic steel frame with S&S couplers and also my Ritchey steel Breakaway.

More examples. When I feel I can afford it, I would like to further lighten my Giant TCR Advanced bike now at 13.50 lb sans pedals, cages and computer mount. The frame weighs a disappointing 1,207 g. When I switch, it will be to something in the 800 g area I imagine. When that happens, I will move most of the parts to the new lighter frame, and the old frame/fork will go bye-bye.

On the other hand, I recently had my remaining custom Romic steel frame (1990) repainted and outfitted with carbon fork and all up to date parts. I plan to keep it forever. Sentimental value and all that. Besides it is damned good looking. So it isn't about age per se. Nothing ever wears out or becomes unserviceable. I just have my own definition of obsolete.

Also bike and wheel building is a hobby for me. I may choose to make a change not because of lusting for a new bike but just to have a project to work on. That is a complicating factor.

Elvo

About once a year according to my LBS's recommendation for crabon bikes.

MikeD1

Just bought a new road bike in Aug. First new road bike in 28 years. Keeping the Centurion Ironman as a backup and will probably take to FL this winter since I don't need wide range gearing there.

dherzfeld

I had this bike as well, bought new in 1988, full Ultegra. Rode it for many years until the current Specialized appeared on the scene, and sold it at a charity garage sale for $75 I believe. The current Specialized is beginning to show its age also, so my eyes are on a new Ti frame / full Campy bike for my 50th bday in 2015, which I intend to ride until.....

StanSeven

Maybe it's time to find a new LBS

Duo

generally as needed.

Shuffleman

Once I get a bike that I love, I keep it. Once I get attached, it stays.

Dave Cutter

An interesting concept. Please tell us more of this "sell your existing bike". I got about 3 & 1/2 seasons out of my original new road bike. It is now my rain-bike and trainer bike (I rode it on the trainer yesterday). I've got a little more than 1000 miles on the bike I bought in July. If I can get and stay at or near an ideal weight for a couple years... I might try a CF. Then, this years new bicycle would become the rain-bike.

I also keep a wall queen old school Cr-mo real steel hanging in my man-cave. But that/those bikes seem to rotate thanks to Craigslist and an agreement I made with my wife.

Sullalto

very much so.

With the stock platform pedals, too.

I'm poor.

I'm also accepting donations of bikes, frames and parts, stack/reach of ~ 600/400mm +/- whatever is reasonably adjusted.

Drew Eckhardt 

10 years, then 17+ although it'd be a frame swap (titanium again, the current one looks better than the painted one before it in spite of a lot more miles) not a sale (I'd do longer chain stays for pannier clearance, eyelets, and S&S couplings for travel)

Replacing worn out parts with newer ones (you know - NOS 2010 Campagnolo Centaur Carbon Ultrashift levers, 2004-2006 Record Titanium derailleurs) is thousands of dollars less expensive than a nice new bike which would be ugly.

Power meters are affordable. Bike computers have configurable displays, recording, and GPS. Neither is a standard feature and both easily retrofit.

We have more cogs in back. Hood ergonomics are a bit better. Velocity offers retro-reflective powder coating on rims. Aerodynamic carbon fiber rims are available when people need to go fast.

Retrofits are thousands of dollars less expensive than a nice new bike, perhaps when cogs/derailleurs/shifters/rims wear out.

Otherwise beyond electronic shifting tech hasn't changed appreciably since 1996 when we had integrated brake/shift levers with under-tape cable routing and dual pivot brakes. We did get things like threadless headsets, but that's more for manufacturers (one fork for all frame sizes) than buyers.

Styling has gotten worse. Even Campagnolo's latest crank looks like a dead octopus. Black anodizing which shows scratches has become omnipresent as a carbon-fiber imitation like plastic laminate flooring pretending to be wood.

Reynolds 

My bikes are steel, I don't need to change them.

merlinextraligh

I tend to buy a bike about every year. But it's typically a different bike; road bike, tt bike, track bike, cx bike, mountain bike, tandem.

This year it was a MTB. Tandem is now 7 seasons old, so a new tandem might be next year's acquistion.

Jaeger99

Wait, you're supposed to change your road bike?

linnefaulk

Next, they are going to say we need to change our socks!

rpenmanparker 

Even when they mess their diapers? Yeeew!

surgeonstone

2 bikes in 43 years, first one is an Italian steel frame, still in perfect condition and ridden regularly, second bought in 2004 and still in perfect condition and ridden regularly. Care for them and they last forever, unless they are carbon of course, then who knows when it will asplode.

powbob

Sell my bike?!!!!!!!

libero

Here's the program I've got:
There are 2 road bikes at any given time at my main home. (I'll exclude my remote home from the discussion for a moment, I do have another bike there which is on a different program).
These are aluminum.
Per my plan, the designed-in service time for these bikes is from 6 to 10 years. If I want to play around before at least 6 years are up, I just think about swapping some parts maybe. (right now, it happens to be pedals on the 2009 bike. After that, it'll be the custom wheels on the 2011 bike, which are actually pretty old rims).
There are too many cool advances to really plan to have a bike much longer.

I haven't spent too huge an amount of money on either of them, but I know I'll be able to get something new before too long. (2009 CAAD spent around $2400, 2011 Viner spent around the same, but I carry over some of the parts that still fit that I still want).

So having this kind of plan ahead of time keeps some discipline on the fun. But also there's a bit of a safety element with aluminum, which will eventually wear out (and I don't want to be on it when it does). And it gives some time to assess all the latest gadgets and breakthroughs before it's time to buy.

StanSeven

Just as often as washing your bibs

DOS

My "highest end" road bike is a 2004 CAAD7 Cannondale. I have added new components here and there and considered upgrading the frame, but everytime I have ridden new carbon, I haven't been so overwhelmed by the performance and ride quality differences that I felt need to drop the coin. C'dale really knew what they were doing when they built the CAAD7 so until I get on something and go "wow", I'll keep,riding it. I have ridden high end carbon of different makes with mixed impressions, some I really liked, some not so much, none enough to make me want to spend money (I don't race). I am curious to try CAAD10 to see how C'dales modern alu compares to 10 yr old offering.

I also have a steel commuter that I think of as my older bike because I bought its predecessor in 2001; it's not really old though, but I never fully replaced the original either. Over the first few years I had the bike, I upgraded components on a 2001 steel Jamis frame, then that frame suffered a warranty failure so Jamis replaced it. Because I swapped components over from the original frame, it sort of felt like the same bike, but it really wasn't because, in addition to new frame, I had changed at least 1/2 of the original components (upgraded wheels and shifters, e.g). Then I got hit by a car and the second Jamis frame -- a Quest, which was great -- was toast. I replaced it with a Soma Smoothie frame -- also great -- using the same components from the second Jamis. So again, because I didn't buy a whole new bike but created one from parts of the original two, my current commuter's lineage goes back to 2001 but really it's a totally different bike even though I never set out to "change".

sevenmag

I only have one bike that I ride regularly. Doubt I'll ever sell it, and probably couldn't get enough for it to put enough of a dent in the price of a new one to make it worth the effort.

OldTryGuy

Built up my Waterford Paramount in 1983, changed to a USA made D/A equipped CAAD8 best friend gave me that belonged to his brother around 2011, was able to register for the 2013 Ironman Florida triathlon and wife said I should get a new bike so I purchased the Propel Advanced SL in 2013 and that could be the last.

TexMac

Every year or more. Within a year and 1/2 i've rode and sold 3 bikes I'm keeping Giant and building a Colnago, gave away my MTB. Will need a TT bike at some point

thermalattorney

I get restless: I'm on my 8th frame in the last 5 years. Plus if you wait for good deals on CL or eBay you can try all the bikes you want without it costing you anything but time.

That said, my current road bike is pretty awesome and I'm not sure what could lure me away from it.

tmh657

^This, for the most part. I may not find a Pegoretti to try anytime soon since I don't have thaT kind of coin. I have sold a few bikes that I regret, that's a long story.

My most modern ride is a 2012 CAAD 10 that I bought so I could fit in with my buddies on modern bikes. Then I found a '96 Serotta Atlanta that was cosmetically challenged and cheap. Built it with 6700. I love, love love it. Then I found another Atlanta that is clean with the Red/Yellow fade. Built it with Record/Chorus 10 speed. I figured I would sell the first Atlanta. NO WAY. It's the same bike but it's not the same. I won't get rid of either one, EVER.

I rode my friends Tarmac SL4. It's nice. It was $7000. I won't buy one. I'm too cheap. The bike I ride most, and with my carbon buddies is the first Atlanta. I think it's because of the steel fork.

I lucked upon an early '80's 3Rensho in baby blue in my size. I don't think I would ever find another so it must stay.