i've reported before on whether or not you should buy a running shoe to fit your foot type. the most recent studies simply do not support this idea.
for one thing, analyzing a foot type, or how it performs when you run, is not as easy as looking at the sole of your shoe. too many variables are at play.
furthermore, just because your shoe wears a certain way, and just because your foot looks a certain way does not mean that the store-bought shoe will alter either the foot's mechanics or the shoe's wear patterns. at least, not without the possibility of creating a new movement pattern that may create new injury risks.
so, in keeping this discussion brief, runners should change shoes frequently based on mileage and running surface; should address the two most common causes of running related injury - doing too much too soon, and the third - on a different surface; and should address any injuries with professionals, either physical therapists or orthopedists AS LONG AS SAID PROS ACTUALLY WORK WITH ATHLETES!!! this is maybe the most important thing to know: not all professionals understand all sportsmen. seek an expert in your area and don't forget - take your old shoes in with you.