I used to cover our previous coach, but it was bare gel-coat with vinyl graphics, and the cover definitely kept the oxidation down.
But, when I started researching a cover for our new coach with full-body paint I found cautions regarding the constant flapping actually wearing through the clear-coat and paint. We have plenty of wind here, and having watched the cover on the old bus flutter constantly, I decided against one for the new coach.
Even with a top-only cover the straps down the sides will flutter and may damage your paint.
My thinking is a good wash, wax or sealer, and tire covers may be the best way to go. And making sure all the window coverings (hopefully blackout) are closed up tight to protect the inside.
2016 Tiffin Allegro Open Road 32SA
2017 Jeep Wrangler JKU