Oddly, no has mentioned that you don't "steer" the bike on rollers. Steering movements are much too large. You just shift your weight slightly. If you get way off course, you may have to steer the bike briefly, but most steering inputs result in oversteering and then you're all over the place. When I started, I found it much harder to look straight ahead and always watched the front wheel, but evidently this is not universal. The trick with the elbow pushing against a support is exactly right. A narrow doorway is easiest, followed by being next to a wall. Starting in the middle of a room is much harder, especially when learning. Not recommended - too much negative feedback bums one out. Go for success, then get fancy. Also, be sure your front axle is over the front roller. Some people prefer to be 1" behind, but I prefer exactly over - never ahead.

If your saddle won't let you sit for an hour, you need to go back to the saddle search. I'm enjoying a Performance Forte Classic. I don't get bored on my rollers. Usually whatever I'm doing has me hurting pretty good after an hour and a half, so that's about it for me. I train on rollers and reserve outside for long rides. If it were snowing, I'd go XC skiing for the long rides. However it mostly just rains here, no biggie once or twice a week.

I don't figure it in miles, rather in hours. Say 4 hours a week in winter. That's enough if it's drills of some sort.