All the time, I did hook up a small propane heater yesterday. Today it is hovering around -27F I believe I will stay inside for this one. I dress in layers starting with silkies, waffle, then down. No cotton. It does take some of the fun out of it a bit though. I have spent nights in snow caves and foxholes using my boot as a pillow. This cold snap has been pretty uncomfortable though. Definitely testing the daily driver's battery condition.