I think the 500 miles thing is nothing more than clever salesmanship. There is no evidence to suggest that it's true and actually one study which proved the opposite (less injuries with worn shoes). The cushioning (in road shoes or any other) doesn't prevent injuries anyway (again, no evidence and some counter evidence) so I say wear them until they fall off your feet. I have inov8's such as my X Talons which are falling apart but feel as comfy as carpet slippers. I do agree that, particularly the newer, Inov8s arent made to last - which is a shame because I love them in every other way.