OP - Sorry your tires were cracking at that age - no doubt about it, the wallet gets dipped into when this happens:)!
Can you share whether or not you exercise your coach, and tires, on a semi regular 4-6 week interval? Or, does your coach sometimes sit for longer periods between trips. Or are you a full timer and put many miles on per month? I'm asking, because how the tire is maintained/exercised, could have a baring on how long it will last.
And just a general comment. Naming a brand of tire, like Michelin, and saying anything about it - is relatively meaningless without knowing the specific model. (Sort of like some driving a Ford Pinto, saying that 'Ford's are slow!' - Well a GT40 owner might have a differing perspective on 'Ford's'...) Specific's matter, and can help others as they research. (Just my opinion:)!).
And tires are very much like Dino vs Syn, or Chevy vs Ford, or (Whatever vs Whatever) - people have different experiences with a 'Brand' - and anyone who does not see the wisdom in using 'that brand' - well, they might as well just move on down the road...
And larger manufactures of any product, have many variants and models - sometimes one will suck. But to say all of the products from that manufactures 'suck' is not always true and or fair.
Ford for example, had the Pinto Fuel Tank issue. Chevy had the Nadar(SP?) Corvair issue. Audi had the false Sudden Acceleration of I believe the early 5000 issue. Michelin certainly had problem with their 'Passenger like XRV tires for RV's, believe this was the famous Zipper Tire. Heck, Ford Explorer's had the evil Firestone tires...
To say everything is bad from a manufacturer from a problem with one product, well...
Many good tires available. Many times at different price points. And lower cost, does not always mean lower quality. And higher cost, does not always mean high quality.
I do have mostly Micelin's (And practicing what I preached above, first set I put on were XZE*'s. Due to a deep sharp edged pot hole I had to replace two tires during a Michelin tire shortage period. Ended up with 2 BF Goodrich ST230, which also seemed to be a solid, good bang for the buck tire. The current set of tires, are Michelin XZA2's.)
My next set? Well, it's out about 5-6 years - and who knows what I'll go with. No problem with Hankook's, Cooper, Toyo's, Bridgestone, Continetal, Yokohama to name a few. I don't shop by price alone, I research and shop based upon several criteria, of which price is towards the bottom of the decision process.
I suspect that if I'd bought a set of any tires, and felt I had maintained and exercised them well, and they started to crack earlier then I felt they should of - yep, I'd be not too anxious to try another of the same 'model' of tire. But I would not eliminate the manufacturer based upon one set of of one model that had a problem...
OK, done rambling. And now excuse me, I must get over to my HiFi forums. Some members are insisting that Digital can sound as good as Analog - well, what are they thinking???!!! (LP's a spinning, tubes a glowing - oh yeah HiFi:)!)...
Best to all, have fun, be safe,
Smitty