I am currently in my upper 30s and I've noticed that I can no longer put more than 300 miles on a pair of shoes. Nearly every day my knees ache both while running and while not running. In my younger days, I was stubborn and put nearly 1000 miles on every pair of running shoes I owned. I ran upwards of 90 miles per week. Is it possible that I could have prevented some of the aches and pains that I have NOW by changing my shoes more often when I was younger?