At one time, my hubby was running 75 mi/wk and I was doing 40. We try to change our shoes about every 300 mi. I highly recommend www.roadrunnersports.com. We've been doing business with these people for years. They are awesome. Hubby has even taken a pair out, run in them, then sent them back because they didn't fit well. They sent him a different selection for the same price. There prices are as much as $30-40/pair below running store prices on a lot of designs, and they continue to carry out-of-date styles for as much as 2-3 years after you can no longer buy them in stores. They get your orders to you very promptly. I just can't say enough good about them. When our closet gets too full, we donate good shoes with too many running miles on them to the Salvation Army or homeless shelter. They are always very much apprectiated.