I've typically been able to run 400-500 miles on a pair of shoes and not notice any signs of wear on the soles. I've always considered myself a neutral runner and wear neutral cushion shoes and flats without medial posts.
I just took a look at my shoes today and noticed for the first time that the midfoot area is wearing down a lot(about 500 miles on the pair). It is the same model shoe that I always wear, its just that this is the first pair that has been worn down on the midfoot area.
Has anyone else experienced this and is this something that I should be concerned about? I do think I am running a little differently than I used to and have noticed that my footsteps are noisier (kind of like a slapping sound on the pavement). I've also been running on grass and hills a lot more, trying to emphasize more drive with my knees and quads, but I wonder if its messing things up.