Many folks have added a catalytic heater that does not require power to avoid running down batteries while ski camping. Also, you can reduce the area that needs heating by not extending slides and using a heavy drape or blanket to isolate the big cold windshield from the living area. Years ago we camped in the parking lots of ski areas, along with several others. Just have to be sure you don't get in the way of snow plows.
Also, you have to evaluate your propane supply. In Breckenridge one very cold weekend we had to make a daily trip to replenish ours (1972 vintage that only had 2 30 pound bottles). Even with a 30 gallon tank our 35' class A with dual pane windows and good insulation had needed a propane fill after 4 days in zero weather.
Also consider the location of your water lines, drain and dump valves. And don't forget the water heater. Have had icicles hanging from mine.