[rohrmann]

We have never winterized our rig, but we full time. Saying that, we have pulled in below freezing a number of times, but we run our heater when doing so. We are lucky that all the furnace registers are fully exposed with the slides in, so there are no restrictions in the heating system. If your rig has fully, or mostly exposed registers, I would think you would be just fine with the heater running.