If appears that steel ply carcass tires like the G614, XPS RIB, R250, Sailon and the commercial 17.5" tires will age out way before the tread wears out. I removed a set of ribs at 6.5 years of service and 40k+ miles because one of them was actually 8.5 years for manufactured date and showing minor cracks. The other three on the ground were 7.5 years old. So I learn to watch date codes!!! These tires still had about 65 percent tread left, and I would have ran them longer if that one had not started cracking.
That brings us to value over time. If these higher cost tires will live two to three times longer than a cheap tire, then for many they are a much better investment. I like that fact that I can get in my truck and tow the trailer to Arizona 1650 miles in 3.5 days and not worry about tire failures! That to me is worth every extra dollar for installing the best tire available verses a cheap product that really has no place on a heavy and tall trailer.
As a side note I replaced the Michelin's on my wife Buick Rainier the other day. They were also most 10 years old. No cracking and around 40K+ miles. Vehicle is always garaged and has an easy life, winter driving is on another set of studded snow tires and rims. I had a 1987 Accord that ran the OEM Michilen's for 11 years. Then had become hard and slippery on web pavement. If I put anything on a sidewall wall of a tire it is Aerospace 303.
Would I run 10 years on trailer tires? No, as they run "loaded" basically all the time. 6-8 years depending on condition is however doable with the right tires.
This brings us to the GY G614's four year warranty period, which one has to be mindful of! Not only is this an expensive tire, it has a pretty short warranty period. Michelin's warranty is 6 years.
Chris