I was checking my main running shoe this morning (bought in april 2006) and the fabric at the heel is starting to fray, actually even torn on the right shoe. The rest of the shoe, especially cushioning, is still quite alright even with a few hundred km use, but I hope that this doesn't mean that I have to replace it anytime soon. I don't get blisters or anything from it. At least not yet. Amazing how flimsy things are nowadays.