Like Louandsal above, I also use a Calmark cover here in Washington state. They are made with Sunbrella fabric which is used on a lot of outdoor furniture and boat covers. I see they now warrant it for 6 years. It is relatively light weight and holds up real well as opposed to some of the covers made with Tyvek that I'd tried on a prior Class C. I can install myself but I don't lift the entire thing on the roof at once. I place it on the ground near the rear ladder and pull up a little at a time until it's all up there and then properly place it. They are custom made and have a zippered door which allows easy access for occasional interior inspections during the winter storage. Mine has been in use every winter since 2008 and it has no signs of wear nor has there been any abrasion noted on the motor home from it's use. I use it primarily to protect the RV from the damaging effects of UV. I'd rather cover than wax more often. Everyone has their own opinion on covering and that's mine for what it's worth.
Al