Paul, most of us use Hawk Blues in the front. In the back, some prefer Blues as well, others, Hawk HP+ (slightly less agressive, but also less risk of rear lock-up). Brake life varies with how hard you use them, wether you run enduros, etc. Rears should last more than a season. Front last most of a season, if not more.
BTW, I bought what was claimed to be a low mileage piston for the motor Jim's builing for you last week. They arrived today, and are at the machine shop being measured. Hopefully they will size out better than what we have now!