This is a topic that I occassionally wonder about as I feel I get a lot of mileage out of my shoes.
I started running again about 5 years ago. During part of that time, finances were tight and I started putting a lot of miles on my shoes. Also, during this time, I have never purchased the same brand or model twice. Now, I still tend to put a lot of mileage on my shoes simply because I learned that I can. Of my last 6 pair of shoes, I have comfortably put 700 – 1000 miles on all of them — averaging about 900 miles. I say comfortably because there were two pair I extended their use beyond what was comfortable. I cut my mileage to compensate for the shoes and at one point, I ran in my racing flats for a week or two until new shoes fit in the budget. My last pair of shoes, some Reebok Premier Lites, I put 1002 miles on and retired them for bad odor as much as anything else. I think I will shop for Premier Lites next time around.
I like to get a new pair of shoes before my current pair is totally worn out so that I can continue to use the old pair occassionally. It is especially useful if my main pair of shoes gets really wet and need some time to dry. After I get a new pair of shoes, the old pair is pretty much retired from long runs, so much of the last 100-200 miles is made up of shorter runs. That probably extends the mileage a bit. Another thing that might contribute to the longevity of my shoes is that I run a lot of miles on dirt/gravel roads.
During this time, I have had only one significant injury and I cannot say that it was caused by shoes. That injury was a bout with plantar fascitis. After recovering, I put an additional 300-400 miles on the same pair of shoes that I’d been running in when I was injured.
With all of that said, I still wouldn’t recommend that someone go out and try to put 1000 miles on each pair of shoes. I believe that another part of being able to use my shoes so thoroughly lies in that I was able to recognize when my shoes started causing me problems and either get new shoes or reduce my running until I could get new shoes.