Winter - A time for preparedness...
Sitting around for the winter? You've got a good time to fix, update, modify, and service your RV... whether it is a motorhome or a trailer of some kind and for those tent campers out there they have time for equipment maintenance.
Keep it up to specs... Don't forget that your RV may be using battery power just sitting there. Keep a trickle charger on the batteries to keep them properly charged. Discharged batteries freeze. That is costly, and it is an unnecessary cost that a little forethought will save. Check the unit for leaking while it's sitting. Water gets into cracks and expands when frozen. Don't get caught with a problem that could be fixed simply with a little sealer.
Motorhome? Run that diesel engine or that gas guzzler. They don't like to sit around for the winter with no use. I run mine once a month and actually get it out and drive it a bit to circulate everything.
Generator? Generators love to be run. They need it! Run your generator during the winter with a load on it so it gets the proper exercise! I usually start up the generator and then start up the motorhome and drive around with the generator running also. Good time to exercise both while under your supervision. I've got Stabil in the gas and diesel so there should be no problem with freezing there. I top off the gas/diesel when I'm winterizing so that there is no room for the collection of moisture in the tanks. The little I use to run things in the off season doesn't really affect that.
Most folks don't make as much use of their RV equipment during the winter and that makes it an ideal time to work on things. You're winterized so the plumbing system is probably not going to be the prime focus although you can install/repair it while it is winterized. And well might you want to consider doing such things then because you're also sure the system is about as 'clean' as it's going to get.
Want to add some fog lights, backup lights, or maybe some interior lights just where you need them? Easy enough to do and there's no pressure to rush to a completion. Organize your spare parts. Organize your storage areas and list what's in each area so you'll know what you've got with you.
Winter is simply a good time to get things done! Wash, wax, and add that protection on exposed parts on a warm day. There's always a lot to do and there's always time for you to relax and enjoy.