I have had three car covers over the years, and did not like any of them for outside storage. I have had 5th wheels, TTs, and TCs since 1972 and none ever had a cover of any kind. I currently have a 1988 Bigfoot TC. I am the second owner, bought it in 2004. It has never been under a cover. Last year, I splurged, and bought a 26'wide x 31'deep x 14' high carport. It was $5000 installed. I park my Bigfoot in one side and my 1987 19 ft Alpenlite 5th wheel in the other side. I guess you could think of it as a retirement home for old RVs.
I will say, covers would be a real hassle for me. Too much drama to cover and uncover. I opted to leave my RVs uncovered, until I decided to deduct the carport from my kids inheritance.
Wayne