I cover my camper for the winter here in NH, been doing so since 2008. Covers aren't cheap, I spend about $350 every 3 or 4 years. I clean the camper before covering it, winterize it and put a bunch of fabric softener sheets in it to keep the mice population down. In the spring, even before I uncover it I plug it in and run an
Eva-Dry Peltier dehumidifier 24/7 through the summer when it's not in use.
In the spring it looks and smells the same as when I closed it up.