We use propane or Kero heaters in the box truck, it's 11 degrees outside and 66 in my truck. I have the option of parking in a heated garage at a Quick Lube place that will let me park inside if we need it.
The only problem with that is i cant access it at night, since we do water damage I like to have it ready to roll.
Is it a PITA? We have to make sure we have enough fuel and a back up heater ready all the time, I keep the remote thermometer near by and check it when ever I wake up during the night, I had to go out in the middle of the night a couple of times this season.
I would rather deal with the heater than take out all my wands and chems and winterize each night.