CptSydor --
While my goal was to have my truck and TC setup to handle whatever weather came my way, be self sufficent, and have all the comforts of full utilities, it took lots of iterations and improvements to get there.
Initially I was like the majority of RVs that you see at various ski areas over a weekend. Fully winterized, lines drained and only using the heater. Basically camping in the TC and using bathrooms at the ski resort.
What showed whether the changes I had made would allow me to safely start using more utilities, in what conditions, was using several wireless (actual/min/max) thermometers and a good battery monitor like a Trimetric. Nothing like data under various conditions with my TC setup vs. peoples opinions on what to do and whether it was effective.
Initially just identify the coldest / vunerable areas inside the TC with multiple thermometers. A FLIR infrared camera would be very useful, if you had access to one, but it is pretty easy to feel the cold drafts, when it is blowing outside.
After finding the coldest spot, then monitor the min/max for the inside temp., outside temp, the coldest spot, along with how many A-hr were used over a weeked under various conditions. A-hr used for the weekend will give you an idea of battery bank size needed. A-hr also acts as a surrogate for propane use, if you are running LED lights. Alternately you can just weight the tanks before heading out and after returning on a bathroom digital scale, or some other way of assessing propane level in the tank.
If you frequent ski areas that have reserved electrical hookups, or you have enough generator capacity to run two 1500W supplemental electrical heaters (one for the basement), you can start using water and see how it goes. Alternately, if you live in snow country, you can set temperature alarms, experiment and gather lots of information in your own driveway. In addition to using the search fucntion on this forum, take the time to talk to the other RVs in the parking lot and ask what problems they have had and how they solved them.
Finally, the rule of thumb for survival when exposed to extreme environments is 3-4 hours. You'll need plans/equipment for various contingencies. You'll find that cell phone coverage is spotty at best for a lot of the highways and roads to ski areas in northwest US and Canada. A SPOT, PLB (personal locator beacon, FastFind or ResqLink) or Garmin InReach will allow you to contact Search and Resque personnel in case of a life threatening emergency for yourself or others.