Here in FL, I look at this differently. A couple of years ago, my wife had a rear (thankfully) Michelin tire blow out on I95. Not nice for her. the tire was 5 yrs old, fairly dry rotted and yes, at the end of its life with respect to wear.
The heat and coral-mixed asphalt are tough on tires hence im keeping a closer eye on any that im running.
I will say though, the Honda I just bought has some '09 BF Goodrich on and there are NO signs of dry rot. they previous owner had them filled with nitrogen, something that Inever cared for and thought was silly, does anyone here think that this nitrogen may have helped these tires not rot?...much younger GoodYears that are on the wifes car have visible rotting??..