When I started the RV lifestyle, I read a lot about "china bombs" and it had me worried. I had bought a used 2005 Glendale Titanium and it had the original tired on it (bought in 2011). The DOT codes on the tires made the tires almost 7 years old.
They had good tread and minimal cracking so I continued to use them for a while. I consulted my tire guy and he said they seemed OK but they really ought to be replaced. At the next season I got new tires and asked my tire guy about "china bombs".
He said that there will always be a few bad tires and switching to a new facility usually makes it worst, BUT he said that tire pressure and speed were more important. He showed me that "Trailer" tires (ST type) had a maximum speed rating of 65 mph!
I try to keep my trailer at or below that speed and as you can guess I get passed by almost everybody. I sort of try to avoid interstate highways because I hate to be in other peoples way. I get passed by lots of other RVers that are flying. They are probably doing 75 or 80 mph. That and a little low pressure and the next thing you know another of those "china bombs" had a blowout.
I had increased the load rating on my tires to E rating from the D rating that the manufacturer recommended and I bumped up my tire pressure about half way between the manufacturer's recommendation and the max suggested by the tire maker. I also have one of the infrared temperature guns that Ray recommended and check the tires at every stop to see if I any issues.
So far everything has been fine but it is about time to replace the tires again. This again will be age based as they still have decent tread left. My next set I plan to actually wear my tires out instead of them dying of old age.
you may want to check the speed rating on your ST tires. I think they all used to be 65 mph but in recent years some manufacturers have made tires with higher speed ratings.
My Goodyear Endurance ST tires, made in the USA, have a speed rating of 87 mph.
Having said that, I usually don’t tow faster than 65 mph.