I camp in the winter at ~8500ft and basically do the same thing as I always do - bring way too much crap. In the summer I can easily walk a mile or two to a nearby cabin, but I noticed today shooting up there that every single 'residence' was boarded up or completely unplowed, and no tire tracks in sight. A blown engine or transmission, failed alternator, or dead battery, could equal dead me (this is always solo, er with my dogs)
That said, I take extra care to make sure everything is tip top on my tow vehicle in the winter - no small feat when good DIY maintenance days are few and far in between with shorter days and weather.
I usually only bring up one pair of clothes for an extended summer weekend. I don't get any gratification out of slipping in to clean clothes when I'm covered in sunscreen, bug spray, and campfire smoke. Winter though... for a 3 night trip, I bring 6 pairs of thick socks, snowboard pants, two jackets and liners, poncho liner, base layer, two stocking hats, extra blankets in addition to 0*F rated sleeping bag, 3 pairs of gloves, hot hands packets, zippo hand warmer, and likely another half dozen things that are escaping me right now.
While I've recently upgraded to a new pop up trailer with 20# of propane and furance, I still carry a Mr Buddy heater and 3 cylinders. Logic is that if negative temperatures and elevation work against me I'll have an easier time warming up a small cylinder than a 20# tank. I also take a 100w flexible panel to complement the 200w of rigid panels on the roof of my vehicle since there's less sun to be captured during the day. I'd kick myself forever if I ran out of juice on the trailer and couldn't run the heater despite having the propane to do so.
That's really it. I figure we (dogs and I) would starve to death before freezing. There's a ton of wood to be gathered up there and I have a few ways to collect/chop/ignite, so my primary focus is staying warm overnight in the trailer and being able to drive out even if my car's electrical is crippled.
What I don't take is my Whynter 62DZ fridge/freezer.. and I absolutely love not having that #$@! thing in the car.