Protecting the tires is paramount and keeping them covered is a good idea. UV and ozone are two of the killers of RV tires. Realize that, even though not used extensively, the tires will probably only last 5-7 years, regardless of how the tread looks. RV tires usually do not wear out, they typically age out.
But overall, you’re probably doing the best by keeping the coach covered while you’re away.