Michelin is having a rough time with 22.5" MH tires. They are having so many problems with cracking, they have published a document with pictures showing three levels of cracking, going from ok to use, to change now. I changed my Michelins at 30k and five and a half years due to cracking. I don't care what they say, I'm not heading out with cracked tires...I've had a RF blowout, and don't want another.
Go to one of the big RV forums, like iRV2.com (https://www.irv2.com/forums/) and check what the readers say about Michelins.