Had them once upon a time. Became more hassle than they are worth if you ask me, especially storing it inside having no benefit to covers at all. They get dirty, wet etc and then you have to store them when not using. Your tires will age out at the same rate whether you use them or not. That of course is my opinion - to each his own.
On Edit - I should mention that storing the RV inside and where we camp it is usually heavy with tree cover, that is the reason we never saw much of a benefit. Since the OP stores his RV indoors, this was the reason for my response. Seems it's not 5 minutes go by til someone on this forum is waiting in the wings to flame your post. Flame away flamers.