Michelin has a very good article reproduced from MotorHome magazine on their website. Click the link below and scroll to the "MotorHome Article" and click on it.
10 years max..but, like above, I inspected my tires in Los Angeles before heading north on I-5. We came over the Grapevine and stopped in Bakersfield. I just happened to notice a crack in the left front tire. It turned out it was almost 5" long and very deep. I hadn't run over anything or hit anything. When we removed the tire, there were many more cracks on the INSIDE of the tire that could not be seen from the exterior. IMHO, tires will crack from the inside out and you will never know it until blow out time...My tires were 5 1/2 yrs old...fool me once....never again.. I replace mine at 6 yrs...many chance it longer than that...your choice....Dennis
Care of your tires