I think, there's just something about how RV trailer tires are treated, that makes them prone to an early demise. Doesn't matter if you pony up for LT tires or not - Sitting for long periods exposed to the elements, pushed to very edge of weight ratings, driven sometimes when not properly inflated, tight twisting when making turns.....These things take years of life away from a tire. Thats why sooo many recommend that trailer tires be replaced every 3 or 4 years, regardless.
When we had an RV trailer, I always insisted on Maxxis (ST) tires only, and they got replaced every 4 years, no matter how good they looked. Never had a tire issue, in the 12 years we had various RV trailers. Still carry Good Sam ERS just in case, but have never had to use it with the RV.