I mount my road bike on a trainer for the winter, and used it extensively for 3 years now. I usually ride 3-5 times per week indoors once the cold and snow (Upstate NY) arrive permanently.

Some suggestions. . .

1) Use a heart rate monitor. It's much easier to gauge intensity - or lack of. An inexpensive HRM is MUCH better than none at all. Nothing fancy needed.

2) 45 to 90 minutes is enough. I usually ride 60 to 90 minutes. Less and you don't get enough of a workout. More and it gets really boring and difficult to focus. 60 intense minutes is about right.

3) You may still need a recovery day after a 60 minute spin with several hard intervals. No overtraining allowed - even in the winter.

4) Entertainment a must. I have a small TV set up to watch. It's fine for zone 1-3 tempo rides as I can watch TV and still catch the plot. When I'm doing intervals the TV provides background noise as I can't focus on anything but keeping the hammer down. Suggestion. . . Intervals during commercials. Set a DVD or VCR up and watch cycling videos.

5) Air flow needed. Get a fan or two going and take your shirt off. Riding indoor is HOT if you're working hard. You'll sweat like crazy no matter what.

6) Even mag and fluid trainers produce plenty of noise when you're really hammering. Wind resistance trainers (like the one I use) are like jet engines when they get cranking.

7) Vary your workouts to keep it interesting. Intervals one night, and a steady spin the next when your favorite show is on.

8) Computers. A rear-wheel-pickup computer is great as it allows you to watch speed and record mileage for your log. Anything to keep it interesting.

9) The biggest obstacle is motivation.