does it work if you're on the trainer?

Mine works all the time.

The phrase is "base miles"

And of course you get basically the same effect on the trainer that you get on the road for any given time and intensity.

The problem with doing the traditional base period training (lots of long steady distance) is that it's mentally difficult for most folks to do that sort of effort on the trainer.

I, for one, am not going to repeatedly do 3 hours on the trainer.

Thus if your riding the trainer, you're probably better off doing intervals, and saving the long base workouts for the road.

I can't take more than an hour on the trainer.

do you guys watch movies on your trainer?

It works. For those of us disinclined to ride for hours in the dark the trainer/rollers work. Far from "fun" but if it is all ya got in ya....

No, but trainers are ok for base hours.

for a given intensity, well, yes. but i would actually argue that 2 hours on the trainer is even harder (and possibly a more effective workout, depending on what you're trying to accomplish) than 2 hours on the road because you never need to stop, coast, etc.

As others have said, yes, the trainer is fine for base miles.

I've done up to 4.5 hours on the trainer. I find base miles difficult to do on the trainer because it is such a steady, lower effort, it is hard to remain motivated. Interval workouts are easier because it at least breaks up the time.

And yes, watching movies or TV helps a lot. I watched The Wire, the entire series, this winter on the trainer. That kept me focused. I also will hit the Red Box up and rent movies on occasion. I generally prefer crappy action movies - Transformers, Captain America... to anything else.

Base hours, yes. My longest sessions are in the 5-6 hour range, and this year I've done some 3 hours and one 4 hour. Right now a regular ride is 1.5-2 hours.

During the season I'll do some hours too, maybe an hour on a given night.

I ride outside too, but the trainer is a familiar place.

I rarely watch movies except on very long rides. Movies tend to be least motivating for me. I usually watch race DVDs (I have maybe 30? they aren't that costly if you get a bunch at a time from WCP, and the long Grand Tour ones are great); I'll watch my own helmet cam clips; and when I want to work hard, I usually focus more on music. There's a very narrow selection of music I listen to on the trainer, mainly stuff from my clips. When I ride hard I don't open my eyes much, and when I do I'm looking down. The TV gets ignored.

As many know I ride a spin bike inside.
I record and watch movies for longer easy rides. For interval training I turn the TV on for some light but don't really pay attention as I am usually in too much discomfort.