The only 5er tire I've ever blown was new -- our first trip in our brand new 5er. I'm not sure of the mileage on it, but it must have been under 500 miles. Goodyear. We pulled into the nearest tire dealer (on the spare) and replaced all 5 of 'em -- bigger tires, 10 ply.
I'd had Goodyears on the previous camper too. I bought it used and never crawled under it to look at the tire age, but we had it for 5 years. You just never know when a blowout might happen. That's one reason I don't drive as fast as I'd like to and stay at/under the recommended speed for curves. "Stuff" happens.