I have heard the 300 - 500 mile range as well. Pretty big range though - 200 miles is a lot of running. I'll give you the benefit of my (painful) experience though. Tried to make some shoes last a little too long (I loved those shoes) and ended up with a two year bout with plantar fasciitis - not fun. Don't know for sure that it was the shoes but I take no chances now - 300 miles and I get new shoes.