I have only got 2 years or so out of those flannel type ADCO covers. Stepped up the the Carver canvas type covers with the 5 year warranty and much better luck, just $600... I had one for my last Class C and just bought one for my new trailer.
https://www.amazon.com/Carver-Class-...01JIVXGP2?th=1
They are heavy (80ish pounds) so you need a method to handle it which I figured out, but would be a little hairy for some that aren't comfortable on the roof.