In the many years I have been reading RV Forums, this issue comes up often. It seems the majority of RVers do not use covers. Some that have in the past say they would never use one again.
It seems the covers last an average of 5 years, but one good wind storm can rip it to shreds.
My 5th wheel is 20 years old, it sits in a storage lot when not on the road. I wax it every two years and wash it before each trip. It still looks like it's new. The roof membrane was showing signs of failure last year so I had it coated with the two step RV roof coating.
My vote is no cover.