I agree with those that say to keep I covered. We kept our 2001 Winnebago Adventurer in a garage almost every day it wasn't on the road. The cost of a cover is far less than the cost of replacement parts for those damaged by the elements.
When we traded in our Adventurer with over 100,000 miles on the odometer it still looked like new. As such it commanded a much higher trade in value. Several friends decided not to buy covers or store their motorhomes inside. It was readily apparent after only a few years. Not only did they spend more on repairs, but they got far less at trade in time.
If you decide to sell your motorhome yourself you'll also likely see more cash in your pocket in a shorter time period. When we traded in our motorhome it lasted less than 3 weeks on the dealers lot. In the RV business that's like a revolving door. The new owner called us with a few questions. He also remarked that he was overjoyed with the condition of the motorhome given the fact that it was over 12 years old and had such high mileage.