I love the RV covers. For three years, I enjoyed watching my neighbor put the cover on his RV. The first year it was funny but as the second and third year came around, it was hilarious watching him wrestle the cover. He finally gave up on the cover after it started to wear through his clear coat on the corners and it was just too much trouble for him to handle. Now, my coach looks better than his even tho mine has never been covered to protect it from the Florida sun and I have no wear spots in my clear coat.
My paint came with UV protection, as does most urethane paint and I wax it twice a year, or more often when I wash it using a wash/wax product. I live on a lake and less than 1 mile from the salt water and my paint has held up fine for over a decade.
I never covered any of my Classic cars either.
When the cover is new, it has very little grit on the inside. As the years go by, it collects more and more dirt on the inside and it is like putting sandpaper on your coach. If you have full body paint, I definitely do not recommend a cover.