I have heard of some people covering they trailers and others say do not cover so they can vent, they are meant to be outside I am talking about the tarp type cover's
Since the laws haven't changed YET - we still have some personal choice so to each his own :)
but IMHE from having a high dollar bra on my last sports car and seeing what the buffeting did to the finish under it... I'll never put anything on my rv - just wash and wax regularly....