Lots of factors when you consider tires- was air pressure regularly checked and maintained, how much weight they are carrying, speed, how long they sit in one spot with weight on them, weather...
I have had very good luck with the Goodyears on a lighter trailer but I did have one let go in the Fall on the TH after 3 years. I was hoping to get longer service than that.
Toying with the idea of less expensive options and more frequent replacement but not sure- I could just about replace six BFG Commerical E rated tires every 12 months for the same price as replacing the G614's every 3 years.
Will probably go with the G614's but I think I am going to try and get the weight off the tires when I park the rig for the winter.