I max out at 90 minutes. Not because my bum hurts, but becasue more than that feels excessive. If I feel the need to go longer, I will find a way to ride outside. I'm usually on the trainer at least four days a week (November-February, March I get the itch to be outside), minimum 60 minutes at a time. TV and music are distracting for me. If I get sucked into TV or music, my HR and cadence get out of whack, so I basically meditate and focus on my heart rate and cadence. I ease the pressure on my derriere by breaking my workout into four sets. Between sets I've been doing 35 and 40 situps for a total of 150, and recently I started doing 10 pushups per set as well. I start the first set in an easy gear and upshift every five minutes. Gear selection during the second and third set varies according to the objective for that day. Fourth set starts in a high gear and winds down to an easy gear.