everything I read tells me that my running shoes should last me about 500 miles or so. I've been running in my saucony kinvaras for about 2000 miles now and they still feel fine. Some wear is evident in the soles but I cant tell by feel. I had a pair of new balance shoes I ran in for like 1500 miles before that and threw them out because this conventional wisdom says that they were past their lifespan - but they still felt fine. How do you know when your shoes are done?