CliffordK

Oh, just a young pup.
It surely has a few more good years in it.
Up until about Feb 1 of this year, I was riding a Colnago Super that I bought used in 82, but probably is a 68 or 69 model.

My "New" bike is based on a used Titanium frame that I picked up for cheap. It is actually a 26" MTB frame that I built up with 700c wheels. The frame is short (height) and long (length), and wide (lots of rear tire clearance). It is a bit odd looking, but the price was right, and it turns out to be a very sweet ride. The total investment was about $400 for the complete bike.



Anyway, I love the idea of no paint, and just wipe the crud off of the frame. I'm still getting used to the brifters. I still have a little more tinkering to get it to where I'd like it.

How you use the bike is up to you. I'm of the opinion to use and enjoy your nice bike, and leave the junker in the garage. But if you have a $2000 to $3000 bike, then security does become an issue, although I suppose with inflation, my old Colnago might be a $1000 equivalent bike, and it has had good use.

Anyway, a few thoughts.
You talked about a 20 year lifespan. Not unreasonable.
Depreciate a $2000 bike over 20 years and your annual outlay is about the same as a good set of tires.
On the other hand, you could buy 3 nice $700 bikes during the same period, so you could go with basic steel, then upgrade as needed, or rust becomes intractable, or perhaps aluminum develops stress fractures????
The other thing is that a frame can last a good long time. So one can always put fancy new parts to breathe new life into a 20 yr old bike. Some things may still be obsolete, but it can get some of the latest gadgets. So, if you buy a $1500 frame, you can keep upgrading it with whatever is new (keeping in mind that some things like dropout spacing, or head tube sizes, or even brake selection may be more limited).

Don't completely ignore aluminum. Also consider something like the Trek 2200 with an aluminum frame an CF seat stays.