First of all, it's downstairs, unheated and uninsulated. Even still, we have to open the windows and door, and in the summer we crank the fan.
The longest trainer ride I've ever done was 5.5 hours, when I was getting ready for Ironman Arizona in 2012 and the weather was extremely crappy outside. Normally, after work rides are 1-1.5 hours. Weekends 2-3 hours. I could NOT ride over 3 on the trainer unless I absolutely had to.
Doesn't have the scenery of road riding, but sometimes putting the time and effort in is the goal. Enjoy your time on the trainer!