Perhaps I can add something to this thread. Retired tire engineer here.
My expereince with tire failures is that they peak in the third year, but you get a solid, quantifiable, indication in the second year. Also, that tire failures are a summer phenomenon. They are virtually non-existant in Nov, Dec, Jan, and Feb.
The earliest production of the Goodyear Endurance ST tire line is in the tail end of its 3rd summer, and the second summer for the second year of production. I haven't heard of any failures, so my experince says the problems that occurred with the Marathon have been fixed