Have a set of 295/75R22.5's 10 years old on the back of my Kenworth T600. I use it to pull our 5ht with with. There still 70% thread on them. No dry rot nor showing any uneven wear. I will be swapping them out in a week or so. Not because I'm scared of them, just found a set of 14 month old tires for $125. each. These will last me longer then I need them. Or I sure hope so.
Now steer tires a different story. I lost a Steer tire a year ago Feb. That tire was only 14 months old. Still think I hit something unseen on the road. That was my second steer tire blowout over the last 40 years. First time was a 3900 mile Michelin steer tire. We got a bad batch of them in 1985. This last one was a Toyo. Replaced both with new Toyo's after that. Got lucky ordered them offline and they were 7 weeks old.
Now if I swap over to a Class A. Not sure I would take the chance of 10 year old tires. But would sure sure run them out to say 7 years. As long as there not showing dry rot.