My feeling is that training for long distance probably shouldn't be much different than training for anything else. I would aim for fitness and speed and you can almost surely do that with sub-hour workouts. I have heard of people riding trainer centuries, and the very idea gives me hives.

Not that you asked, but my ITB problems cleared up with swimming. Cycling is not known for helping ITB problems

What 1000k are you planning on riding? I wanted to do an early-season 1200k last year, but decided against it.