I made a living on the road with trucks and trailers. ST class tires were avoided at all costs in this type of work.
Label me any way you want but quality tires were all day every day important to make a profit or go bust; pun intended
From Carlisle ;
Time and the elements weaken a trailer tire.
– 3 to 5 years is the average life expectancy of a trailer tire,regardless of mileage.
– It is estimated that in approximately three years, roughly one-third of a tire's strength is gone
– After three years, depending upon storage and conditions of usage, consider replacing trailer tires even if they have tread depth remaining.
– After five years, trailer tires should be replaced in all cases.