Here's what I always answer regarding RV covers. We have stored our RVs in a 300 space outdoor RV storage lot for over 20 years. I see new RVs come in to the lot and for the first year the RV owner will cover their RV. After the first year I rarely see the RV covered. I would guess over the 20 + years there have been about 80 RVs where they are covered for the first year or so and then you never see the cover again. Of the 300 RVs on the lot only 10 or so ever have covers at any given time.
I think it ends up to be too much of a pain in the --- to put on and take off the covers.
Our first TT we had for 16 years, our current 5th wheel we've had for 22 years. Neither one were covered and sat out in the Southern California weather 6 miles from the ocean (salt air) 24/7. I wash my RV before each trip and after the trip if we camp at the beach and wax the RV every couple of years. Both the 16 year old and the 22 year old still look new when washed and waxed.
The edpm roof on the 22 year old is just now needing to be replaced or a new coating spread over it. Otherwise there has been no weather related issues with either RV.
My vote is for no cover...