Currently, we have 46,000 miles on our tires that date from late 2013 and to early 2014. I will replace the tires at the end of next year as they will be almost 6 yrs. old. My estimate is that we'll have about 52K-55K on the coach at that time.
We are heavy at 55,500 lbs. and I don't want to run the risk of a blowout, just not worth it to me.
I have my coach in for service now and the guy is going to look at my tires up on a lift to see if there are any obvious exterior issues. He will also check all suspension components, hoses and belts, etc. :)
Safe travels,
MM.