Most competitive runners will replace their shoes about every three months. Consider buying a new pair of shoes every 300 to 400 miles, or after you notice significant breakdown on the mid-sole or the uppers. You’ll most likely notice a weakening or loose feeling in the shoe when it begins to deteriorate to a point that suggests replacement. Don’t let a beat down pair of shoes cause you a loss of efficiency, or even injury. A new trend in distance running is to own two pairs of shoes. This allows you to split up the mileage between your two shoes and alternate days to give each pair time to “rebound” back into their optimal condition. While the preliminary costs may make this option sound expensive,you may actually get a longer life out of both pairs of shoes, save some wear and tear on your feet, and improve performance.