UPDATE: I wrote to Brooks about what happened to my 12's and they sent me a free pair to make up the miles I lost from them wearing out quickly.  I will definitely be purchasing the 13's because, like I said in the review, the cushioning and comfort of these shoes is second to none.  As a loyal glycerin customer, I was disappointed with these shoes.  These are my fifth pair of glycerins and I have loved them for their superior cushioning.  The 12's are no exception, but they wore out EXTREMELY fast.  The soles were worn away at only 200 miles, and now at 250 they are unwearable due to lack of cushioning and the soles being worn to nothing in some spots.  I am a grad student, aka poor, and it gives me physical pain to spend so much money on shoes, but I always did it because Brooks made quality shoes that were worth it for me, because I supinate badly and needed the cushioning.  I hope the 13's have better soles!