After 11,745 miles it was time. The tire was showing a wear that I had not seen before, slight cupping on both sides with center HIGHER than the outer edges. The wear was more pronounced when the tire was dismounted. By the way it came off hard and the new went on hard, I must have used 5 tire tools and 3 rim protectors and chased it around the shop floor 3 times and more than a few very bad words.