I know this is really early to be asking questions about the off season, but I'm going to anyway

I'm both dreading and looking forward to the off season. I dread it because I'm afraid I'll lose a lot of my ability, but I'm looking forward to it because it means I can hit the weight room and work on my power. Is there any rule of thumb as to how long one's off season should last? And how much riding should be done on the off season? I figured I'd still ride 3-4 times a week, if only on a trainer, just to keep my lungs in decent shape, but I don't want to overdo it since I'm going to be lifting too.

And what about cross training? I know it's generally considered a good thing, but I don't know since I'm specializing in biking, if it'll affect my form in a bad way. Would swimming be a good thing to take on over the winter, or should I stick solely to the trainer? What about running?

Thanks for any help you can offer.