Suntiger and all, I learned when I was beginning to run and training for long events (half marathons) that when something starts hurting -- knee, hip, foot -- check your shoes. I was surprised how quickly my shoes wore because I was previously a non-runner and sneakers lasted me for years, not months. It's been an adjustment in my 40s and 50s to pay attention to the support of my shoes, and I think it gets more important as we age. Shoe wear does't always show in the treads -- support can definitely break down inside the shoe even when the outside still looks serviceable!
I do notice that now, since my ratio of running to walking is very different than it was (these days I'll run a mile or two but walk anywhere from 3 to 8 miles), and I'm on dirt trails more often than pavement or asphalt, my shoes do last a bit longer. I think the combination of harder surfaces, more impact from running, and my supination really made the uneven wear (on the outside edges of my shoes in particular) more pronounced more quickly.
I mention this because I think it applies to not just athletic wear but general use -- some of us are city walker types, others may be on their feet more but standing more. Supination and pronation can cause wear that is uneven and makes us more susceptible to discomfort or injury quicker. In my experience, if I think my shoes may be getting old, they almost always are!
(It doesn't help if you habitually get your shoes sopping wet like I do, hiking through shallow streams and slipping in muddy banks trying to take photos, LOL)
