When you add new gear such as a pair of shoes and you add that to the activities that you have completed it should show you a total of distance based on that information. I run and will replace a pair of shoes around every 400 to 500 miles. I have to manually add those distances up on the activities from a custom date range.
When I look at shoes either in a mini-view gear widget or full page gear, I see the current mileage for that pair. But I have a max distance for each pair I use. The mini view and the full page also show a graph of current distance vs max.
