I have had Michelin tires for years on my first coach, on my current coach, and my tow and have never had problems with dry rot. Any tire can suffer from the UV rays of the sun if not covered properly. I do not think the CW knew what he was talking about or he had other tires he wanted to sell/get rid of. If your tires are 7 years old they need to be replaced. I have mine inspected at 5 years and replace them at 7 yrs or earlier. The price of new tires is cheap compared to the damage a blow tire will cause.