After rebuilding my road bike last year I started using a gear tracker on www.mapmyride.com I have been tracking my tires and drive train. The tracker lets you add the piece of gear that you want to track for replacing. When you add your piece of gear. You are able to pick brand/model, date of purchase, how much the item cost, and projected amount of miles that the item should be replaced.
I just replaced a set of Maxxis Detonator tires. I have been riding them for 1 1/2 years with a total of 1160 miles on them. The gear tracker also lets you know how much it cost per mile to use the tire from your purchase price. From my purchase price it cost me just 0.06 cents per mile.
You can track almost any type of gear that you want. From bike tires and drive trains to running shoes. Using the tracker helps me with pre & post ride bike checks and with planning and budgeting for that next gear purchase.