Actually, Dave's right, who are your vendors? Developing a trusting relationship with your chosen tire vendor is very important. They ahould be able to recommend the correct tire compound and profile for your bike, and tell you at which tracks the tire wear will be the greatest, how long each set should last when ridden at an aggressive pace, and the pressures you should be setting for your particular application. If you show them your worn tires, they should be able to give you some hints about how to extend the life of your tires, which can in turn give you feed back on your suspension set up and riding style.
So much from two rubber (well, not really anymore) doughnuts. ;)