If your TT looks good as the day you bought it when you trade it in, you either used it very little or spend a lot of time maintaining and polishing.
We bought a gently used 3 years old Dutchmen TT and put 40,000 miles on it in the next five years. While it is true that washing and waxing makes it shine, there is no way to hide the accrued damage of active use.
I like the cover because it helps keep the ice and snow from direct contact with the roof. But I keep in mind that TTs depreciate very rapidly, regardless of the care and effort I put into it.