The Life of a running shoe is directly tied to 3 factors:
1. The ratio of softer materials to harder carbon rubber.
2. The actual weight of the runner.
3. The biomechanical efficiency of the runner.
If anyone would like me to provide more information, just tell me so and I will. No need to spend the time, if there is a low level of interest in this topic.
Kindrunner.com is the first socially responsible ecommerce site for runners. When you are done with your shoes, please to not throw them out. They end up in a landfill, where they sit for 90-100 years. Trade them in for new shoes and receive $10.