I'm with Dennis 100%. I just had all mine replaced this morning, 10 years old with 15k miles on them. The guys said they had never seen 10 year old tires in such good condition, and proceeded to say that's also what fools people. All you have to do is stick a fingernail into the sidewall between an old and new tire and you can tell the obvious difference.
Just think about this.. When your 10 YO tire shreds and takes out 4' of your motorhome, what's cheaper.. Replacing tires or a $15k+ repair?
BTW- go check out FMCA's Michelin tire deal before you buy
Jeff - WA6EQU
'06 Itasca Meridian 34H, CAT C7/350