Wait, are we sure that's a good thing? Five hundred miles on one pair of shoes means the cushion and support are totally gone. That's a great way to get a stress injury. Modern materials might not fall apart as fast, but they stop protecting your feet and joints long before the outside looks bad. I'd rather replace shoes more often than wreck my knees.
My old hiking boots fell apart after 200 miles on the Appalachian Trail. It's impressive how much modern shoe materials have improved. Getting that kind of distance, especially on rough terrain, really shows the quality.