I under stand that when the tire material is compounded there are various anti-oxidants, lubricants, sun blockers etc added to the material. These compounds work to the tire surface during rotation.
This works fine for normal auto/truck application. However most Rv's sit idle for many months at a time. This is why the sidewall/tread ages prematurely.
Check on some tire manufacturers web sites for more specific information. I think that 6-7 years is the average time that the manufacturers recommend for replacement.
2005 Dodge, 2500, auto, 2wd. Pac brake PRXB. CB, Max Brake Brake Controller, Rhino Lining, Aero 60 gal. replacement tank.
1998 Hitchhiker ll, mod#31RLBGBW, RBW L'tl Rocker Hitch, Generac NP50 G generator