I used to think rides more than 30-45 minutes were unbearable on the trainer. At some point I started focusing on what I was feeling - much of the time, especially when I'm going hard, I have my eyes closed. I listen to music and think about contact points, form, etc. Suddenly my tolerance for long rides went up a lot.

Without loud music pushing me I find it difficult to ride hard. Movies/clips let me ride a while but I can't ride hard when I'm distracted like that. To wit - my last ride on the trainer I did 125w, 125bpm, mid 80s rpm. A hard ride for me might be 145w, 145bpm, 90-ish rpm.