I removed my plumbing for that very reason. Often I will run the furnace with the top down while I am away or driving to keep the inside of the camper from freezing. Works quite well and with the top down the camper seems to be surprisingly well insulated.
Thanks for giving your experiences...just draining the plumbing during the winter rather than removing the plumbing is the way we go; greatly enjoy having water on-board during at least 8 months of the year during our off-road travels and I would worry about running the FWC furnace while on the road simply due to wind entering the outside furnace box vents at highway speeds and blowing out the flame; BUT you seem to have successfully left the furnace on while driving...interesting.... and empirical knowledge is the gold standard!
Edited by Wallowa, 07 October 2020 - 08:14 PM.