Our kids got us wheel covers as a gift and we use them when we are wintering in AZ. Partly for the sun aspect, but also for appearance (don't you dare say that is a typical response from a woman. )
When we are all set up with our patio, awning, lights, chairs, etc, the wheel covers help with the clean appearance. When we are doing real camping we don't use them.
So far we haven't kept an RV long enough to replace tires. Sigh. We keep upgrading, but we have sworn that the 2016 we have on order will have to last ten years!