Tires have oils in them that when driven on release those oils and help lengthen the lifespan. In storage for long periods you might see a marginal benefit with covers if they are in direct sunlight. You won't have any benefits using them on a camping trip aside from the exercise you'll get putting them on and taking them off. Even in storage any benefits would be hardly measurable. RV tires age out long before they wear out, covers or not. Usually about 7-8 years. When I first started RV ing 20 years ago, I bought a set. used them about 3 x. Never used them since and haven't seen any difference. Covers can also trap moisture in your wheels and tires which isn't good for them either.