Just ran into this article from Self magazine. Just thought it was a good reminder that as much as we like a pair of shoes it might be time to get rid of them for our body's sake.
1. You’re feeling more aches, pains, and other unpleasant occurrences. When this starts happening it might be your first indicator to consider the next two signs,
2. Your shoes literally look a little worse for wear. Remember to check each part of the shoe (Outsole, Midsole and Counter) and if any are worn out, time to replace.
3. Your shoes hit a specific mileage. Over 250 miles start paying attention to them more. (Edit: people are saying 250 is too low. I didn't say replace at 250, I said that the article recommends paying attention to them more. It did say that most last about 500 miles. Just trying to keep it brief.)