Ihave a 29 ft 5th wheel that pretty much stays in one place year round . I also have a truck camper that I purchased new in 2014. I live in a cold climate & have to drain all my tanks in both units , then blow out the lines with a compressor & finally run plumbing (not automotive) antifreeze through all my supply lines & allow some to go in all the drains so that the traps are filled below the sinks. If I want to use either of these rigs in the winter I don’t use the drains unless I add some more antifreeze & I don’t use the supply lines at all. Condensation can be a problem because the warmer it is inside the unit that warm air in contact with a relatively cold surface such as a window or a wall that is not as well insulated & there you have moisture condensing on the cooler surface. I was planning on heading south with my truck but have to postpone for now but I would only dewinterise it once I was safely far enough south .