17 years of experience and hundreds of nights FWC-based skiing (lift-served, touring, ski mountaineering and some XC), first a 2000 Hawk, then a 2014 Hawk, mostly in the PNW, almost always self-contained (i.e., no plug-in). Indeed, I do not recall ever plugging in when parked at a lift-served area. We live in central WA and have done camper-based skiing throughout WA, MT, ID, OR and a few other states. Roughly 50% lift-served, 50% touring/ski mountaineering, December into June most years, sometimes July in big snow years.
Lots of good advice here. My contributions (not complete):
-- I concur that condensation control/moisture management is a major issue. We daily remove thermal liners and wipe canvas with a ShamWow-type cloth. In colder temps, this requires running the furnace to melt frost (i.e., frozen condensation).
-- DIY Reflectix covers for all windows, attached via velcro, significantly reduces furnace use. IME, it's a game changer for winter camping.
-- IME, furnace fan is, by far, the biggest draw on batteries. (Note that our 2014 Hawk has a more energy efficient fan than the one in our 2000 Hawk.) My wife and I (long-time mountaineers and backpackers) seldom run the furnace while sleeping, instead relying on high quality mountaineering down sleeping bags, sometimes zipped together.
-- I remove the water pump and purge the water lines before each winter, carrying water in jugs during winter
-- We carry a lightweight step ladder and snow rake to remove snow from roof. PNW wet powder is heavy!
-- Part of our moisture management strategy is use of a hitch-mount luggage carrier, which doubles as a porch. Use a wisk broom to remove snow from boots, etc. before entering camper. We plan to get a stormworthy free-standing tent (tall enough to stand up inside) to place outside the door for use as a "mud room" for putting on ski boots, etc.
-- We carry our skis in a DIY 1000D Cordura bag that we strap on our hitch-mount luggage rack. It slides under the truck when we get into position.
We get out alot. It'd be fun to meet up with some other WTW skiers!