So here is a case in point. On my last trailer I ran the original tires for 12 years and never had a failure. Yes 12 years; well past their expected life span, however, they didn't show signs of old age cracking, etc. Had one tire that got a nail in it, never exploded, I plugged it and ran it.
So what does all this prove, nothing. Luck of the draw is just as likely the culprit as anything. My current trailer has the original tires on it and I will continue to run them until they are not suitable for the road. That could be 2 years could be 10.
I'd be willing to bet there are more people running their rigs with the original tires from the manufacturer then those that replace them. And how often do you see one beside the road with an exploded tire. About one out of a thousand RV's on the road. I have personally only seen 2 in 20 years of RVing; and who's to say those two were even made in China tires.