We used to, when our camper was stored in an area quite sheltered from wind. At our current home, it's very windy, so we leave it uncovered. (It's also less snowy here than in our previous location.) We used an ADCO cover that was good for blocking moisture from the roof, but had breathable sides. When we covered it, we left the roof vents open (under MaxxAir vent "hoods") and also left one window cracked open slightly. That really helped minimize condensation inside. We still have the MaxxAirs and leave the vent open in the bathroom over the winter.