As your shoes wear, it can be helpful to modify them. Your natural thought might be to add shoe goo and cushioned insoles to the worn spots, but consider going the other way, especially if the wear is more pronounced on either the inside or outside of your foot.
In my case, I get some wear on the outside of my heels, even though I try to use a forefoot strike. When my heel becomes worn on the outside, I then trim the inside with a knife. This allows me to continue wearing the old shoes, and I feel it actually improves the mechanics of my gait and foot strike.
