My legs, especially around my knees, and feet will tell me when its time to replace my shoes.
When I was heavier, I had to replace them more often, mainly due to needing less and less stability as I lost weight. I'm now in neutral shoes and I rotate between two different pair as a recommendation from a more experienced runner. This has seemed to help with the life of both pair as well.
I don't believe any shoes are built to last over 400-500 miles, but I do know some runners who can keep going in shoes until the soles are worn or there are holes at the toes! I think in those situations, the runner doesn't feel any pain or difference in stride as the cushion/form/last of the shoes break down, so they figure they can keep running and running. For those people, they probably do feel like their shoes are built to go well over 1000 miles.