Q: I have a question about shoes. Specifically, when do I replace them? How long are they good to run in before they begin to break down? I know when I feel like I should get new shoes but is there an average shoe-life time if I’m running 4 days a week from 5-15 miles each time?

A: Thanks for your shoe inquiry. The industry standard for replacing shoes is 350-500 miles. Some get the upper range, some get the lower range. At 120 pounds, I break mine down in 350 due to my biomechanics.

In addition to biomechanics, other factors influencing shoe replacement may include: 
Ball-of-foot, arch, heel, shin, knee, or hip aches; surfaces you run on; shoe type; original quality; other activities the shoes are used for; exposure to extreme temperatures and general care of the shoes.

Here’s the info you provided: 4 days a week from 5-15 miles each time. 
And here’s the math: 
4×5=20 miles/wk = 80 miles/month x5 months = 400 miles. 
4×10=40 miles/wk = 160 miles/month x2.5 months = 400 miles.

So your shoe-life range at 5-10 miles per day is 2.5 to 5 months. 

Hope this helps. Thanks again!