I think as long as comfortable to wear and physically well, no need to replace the mainstay of sports shoes. Apparently, sports shoes also have a period of "retirement", especially if you regularly wear them for exercise. Sport shoes which faithful to accompany us exercise, especially running shoes, will lose their balance and ability to dampen vibration or shock. If determined to continue to use this would risk causing injury to muscle and leg pain after exercising. Therefore the best solution is to replace your sports shoes on a regular basis. A podiatry -health foot experts - gives tips about the life of the shoe. For running shoes, replace every 350-450 miles (700 km) usage. Because most people never calculate the distance already taken, the distance is equivalent to nine months of the use of shoes on the runners which regularly practice. As for casual walking shoes, Assume you walk about 5 miles every day, then your favorite sneakers should have retired in the ninth m...