I also use mine for traveling for work. I have been in CO, NJ, NM, MA, GA and currently in NC. All weather at all times of years and have not had anything freeze to date. We stay in parks that are year round and don't require us to use our fresh water tank so I can't comment on that part. The heated underbelly has kept everything warm enough not to freeze. A simple heat trace on the fresh water hose keeps it from freezing. We also skirt the camper with something to keep the wind out during the winter. Currently, we are using 'silt fence' to do this. It is not insulation but keeps the wind out. Even with out this, it's not a problem, just a little cheaper on propane.
Fulltimers? Loving our 2012 36RL towed by 2016 Ram 3500 DRW Longhorn Crew cab with auto level system.