About 4 hours is my longest indoor ride. It was years ago, and I was doing a lot of base building work. I remember that day in particular because I was on Season 3 of The Wire, and I started by watching episodes 9 and 10. I really wanted to see how it ended, and I was limiting myself to only watching it on the trainer - sort of an incentive to ride - so I stayed on the trainer to watch episodes 11 and 12 to finish the season.
As for my training, I think I am maturing. I opted to skip today's workout. Sunday was a rest day, but I some how aggravated my knee on Saturday. It was a bit swollen and sore yesterday, so I iced it and did my normal care routine. When I woke this morning, it was still bothering me, so I am skipping my workout. In year's past, I would have worked out through the pain, stressing about how missing this a workout today would put me behind 3 months from now. But as I get older, and the injuries seem to pile up, I'd rather skip a workout, let my body heal, and come back ready in a day or two.