[ItBites]

The life of these tires will vary with use. The flexing action during use will reduce the rate at which the polymer chains cross-link. Sitting without flexure will allow the cross-linking to occur at its maximum rate for the conditions of storage (temperature, humidity, UV, and ozone). Unless you use UV plant-growing lights in your garage or have a big electic generator producing ozone, You are seeing the natural life of these tires when they are not flexed frequently. As some have said, they get more life than you got. I would think this may be due to the frequency of flexure of the elastomer.