As a lifelong runner it's best to do it by mileage not age. Replace them somewhere between 300 and 600 miles (your weight, leg length, form, surface, etc. all i

As a lifelong runner it's best to do it by mileage not age. Replace them somewhere between 300 and 600 miles (your weight, leg length, form, surface, etc. all influence this). I will add that over time historically the midsole foam usually degrades so age is a factor too. I'd probably suggest tossing them after 1.5 years or so or at least having a fairly fresh pair to compare them to. The above mostly applies to running but should be relevant for walking too.