I recently went to Road Runner Sports (luckily I live in San Diego and can go to their store) and got some new running shoes (GEL Kayano X). I had been developing a little bit of discomfort in my left foot so I also did a gate analysis and found I was running in the right type of shoes. So, I guess my old shoes had just reached the point of replacement. One of the new things I was told during my analysis, was that "typically" running shoes need about 30 hours to "recooperate" from a run and completely go back to "full support mode." So, I either need to get another pair of shoes for back-to-back running days or start doing an every other day routine.