The "Everyone's" we have talked to have all been RV dealers and a manufacturer.
And what interest do these have in you doing something that protects your TT/RV therefore making them last longer? :h
In my area, lots of people cover theirs - can see this in the RV storage yard where I keep mine. Also can see the ones parked in driveways and side lawns in my neighborhood that are not covered and can see the dirty deteriorating condition that they are in.
So listen to your dealer or manufacturer and don't cover, they will be more than happy to sell you a new one :P
Me? I'd rather listen to the folks on have been there and done that and base a decesion on these responses, whether they agree with my point of view or not.