Recently I bought new shoes for walking the canyon and walking my dogs. They're exactly the same as the last pair I bought at REI, the mecca for All Things Outdoorsy. That's my old shoe on the left; the new is on the right:
Looking down from the top, there's not too much noticeable wear, right? But the back view is another story. Here's both left shoes, and this time the old one is on the right:
(Why do I keep flipping the old/new shoes around? Sorry.) Now you can see the shocking difference: I've totally ground down the heel of the old shoe (on the left, below), compared with the new one on the right:
Apparently I've got a wicked left-foot heel strike. These shoes only last me a half a year or so, with the beating I give them. The nice folks at REI told me so, because they record all my purchases in their computer.
Before I could feel bad about being so beastly to my shoes, the nice young man said to me, "Half a year is about right, for really active folks like you."
I floated out of there with my new shoes under my arm.