I regularly camp to -20C/-4F and sometime colder up here in Ontario. Want to run your tanks all the time? Electric tank heaters. Like these
Ultra HeatThat way if your out you can use electric heaters and cut down burning through propane. Those little hoses into the belly of the rig from the furnace do for the most part almost nothing. Trust me on that. Never mind running the furnace full time to keep the heat down there.
Depending on where you go you can skip using your own tanks and use the park facilities. I hate doing that so I use mine. Have a Flojet macerator to unload my tanks at home as well as some parks dump stations are snowed in on occasion.
Lots of fun!!!
Love winter camping. Only a few hardy souls and no bugs :)