If you use a trainer, how do you decide how long to work out?

Saddle time, means the amount of time you actually spend in the saddle according to the bicycle computer.
Clock time, means that you go from a certain time to a certain time.

If you sometimes go one way and sometimes another, I have allowed multiple options to be selected.

I checked 'see comments', as I do whatever workout my coach has assigned. I don't go near the trainer unless it is an assigned workout, and then I whine about it.

My head exploded when I read the second sentence so I checked see comments.

To an extent, I like riding my Kreitler rollers with the 4.5 inch drums with allow caps with the fork stand and Kreitler fan. Key to making riding indoors more enjoyable and a good proxy for the road is to have a lot of inertia when you are riding the trainer or rollers and it is very smooth and quiet. I use a heavier rear wheel to increase the inertia of the rear wheel. One of the reasons (there are many) that riding a trainer is tough is that it simulates a hill. As you put in power via the pedal down stroke, the lack of inertia of the trainer causes the rider to put in higher peak power to maintain the same average power while maintaining a speed. Hence a trainer feels harder (perceived effort) than the road.

With the 4.5 rollers with alloy caps and a heavy rear wheel, the power input is pretty smooth and pedaling feels like the road. In fact, it feels similar to riding the wooden track at the Home Depot Center Velodrome. The Kreitler fan is adjustable so I can select how much wind load I put on the trainer and direct the fan at me in addition to another electric fan blowing on me.

So depending on what workout, I ride the rollers for the prescribed time and intensity. Most workouts are going to feature a sustained z3 or z4 power effort for a specific duration. If I am doing z2 endurance efforts, I do them for 20 minutes and then take a 3 to 5 minute easy spin, get off the bike or etc.

For the next few weeks, I am doing leg workouts in the gym. Immediately, after the leg workout, I get on the rollers and execute an interval routine designed to compliment the weight workout. It would not be as convenient or effective to do that on the road. Pedaling drills are best done on the rollers.

Hating or liking indoor training is about mindset. I can hate anything if I choose to do so. If I convince myself it is good and try to focus on the positive, I can make training indoors tolerable to good. I like to listen to the Shakira radio station on Pandora while riding and focus on posture and perfect pedal stroke execution.

I ride the trainer or rollers for easy spin days, hard intervals workouts, long Z2 or Z3 intervals and for different pedaling drills including OTS. The workouts are usually time based and can take up to 2 hrs. I will also, on occasion, ride the trainer or rollers for 1 hr @ Z3 early in the AM prior to eating in order to teach the body to utilize fuel from fat. Beginning in December I will take my trainer to an indoor cycling class where we will do a variety of drills and intervals designed to produce a smooth and strong pedal stroke from various cycling positions. Last year at the end of the 3 month program I was able to maintain a cadence of 205 rpm for 15 seconds and could hold 190 rpm for over 30 seconds.

Hermes summed up indoor training pretty well. I don't have a fan on my rollers but fold up a towel under one of the rear rollers to produce resistance and use the watt meter to gauge effort and track cadence. Due to the efforts needing to be constant to maintain force on the pedals the first couple trainer and roller rides is a wake-up call to the body. IMHO, Indoor cycling is a perfect time to become a better cyclist, it just takes a good plan and not 1 hr repeats of the "same old, same old".

When I use the trainer - err . . . - I ride to a Spinerval training video. However long that video is is my length on the trainer that day (or sometimes less).

I only set a bike up on the trainer when it is not possible to ride.
Then, I set a timer for as long as I think I can stand it and try to tolerate it for that long and no longer. While watching TV, comfortably reclined on the long wheelbase 'bent.
Hermes and AJ describe actual training while I am just putting some time in on a trainer.

I'm fortunate in that I rarely have to use my trainer. I'm able to get my workouts in during the morning hours 7 days a week. When I do need to use the trainer I can only take 1 hour period.

I get in the saddle and start pedalling lightly. I start the music. I start the clock. I go for one hour.
I get a good lather going then I spend 20 minutes of progressive effort and/or intensity.
I start gearing down and cooling down for 10-15 minutes until I get back to a light spin and an hour is up.
I get off the bike.

e) none of the above. IMO, all of the listed approaches are a waste of time. Every ride on the trainer should have a specific objective and follow a structured workout. Otherwise, why bother?

SP
Bend, OR

I use a Computrainer so I load in a course and try to complete it - x number of miles. For longer courses I put a movie in the dvd player and watch while I ride. Doesn't necessarily make for my best effort but at least I get the time and distance in.

That depends on your objective, distance and time based workouts are good when the purpose of the trainer is to keep from losing momentum. Where I live, the outdoor riding season lasts from roughly the end of May to Canadian Thanksgiving, yeah to can stretch it a little on each end, if your lucky, that means roughly 4½ to 5½ months. This means that if your unlucky and get started May 24 weekend, it's mid-September before your into doing decent distances, and then your done a month later. If you use a trainer to keep up your momentum, then you get the whole summer to get in decent rides.

I follow the Mike and DeDe Barry book, and the Dirk Friel book on indoor training plans. I do some runs from Arnie Baker's book "Smart Cycling" - those are harder.

I use a Kurt Road Machine.

We don't have that many days down here where we can't ride during some part of the day providing you don't mind riding in chilly weather. Our really cold days start off very cold in the mornings but end up having tolerable riding weather in the afternoons. Sometimes this does not happen, so I put the bike on the trainer and ride about the same distance that I would if I were riding outdoors. Last year, I think I logged around three to four hundred miles on the trainer during our winter season, but I was only riding about 15-20 miles a day back then. I'm hoping that this winter season will be a mild one and I won't need the trainer at all. So far so good, as the temps are still in the low to mid 80's.

The only thing I do on the trainer is intervals, either max effort or max cadence. I go for 1 hr with some warmup and a little bit of cool down.

This is the trainer we used for the cool down during the Cyclocross last Sunday here in the San Diego Velodrome. I'm making sure that Lily doesn't spill any of the smoothie she was making. I'll have the same setup (margaritas!!!) for this Sunday's Velo-Swap again at our velodrome. The trainer is a one-off made by Saris (Powertap) the rep me let borrow for the Velo-Swap.

How many watts does it take to make a smooth Margarita? You sure that no Child Labor Law was broken while making adult beverages?

I usually do:
15 min @ 204W
5 min @ 300W
5 min @ 207W
20min @ 275W
5 min @ 175W
20 min @ 275W
10 min @ 175W
Works out to 1:20 and it's all I can take on a trainer. I only do it 5 or 6 times in the winter when the roads are icy.

Nice... Which power meter are you using?

There was no alcohol involved. All the kids wanted to make smoothies and I just used their boundless energy for a cool refreshment.

I go until Coach Troy tells me that I can stop.

Pretty much the same here. The suffering, er "fun", seldom lasts over one hour and is done in company of chums.

I normally ride solo, for a certain period of time, divided between fast spinning and gear pushing pretty evenly. Intervals and variable effort seems to work for me best.