I was looking at covers too... but in the end decided not to get one. I was afraid the cover might do more damage that not having one. Our camper also sits in the woods year round and was afraid that under the cover might provide safe harbor for some sort of varmitt.
My BIL has the ADCO cover and says it works ok. It's a pain to put on and take off. The only negative thing I've read about them is that in heavy winds they tend to chafe the unit a bit where they flap. Keep in mind that I have no personal experience I'm strictly speaking from second hand experience.
Salem 29RKSS Pushing a GMC Sierra 2500HD!
Gotta go campin!