All down to useage Bruce. Track work will kill em. Combination of heat pumped into em from brakes and lateral loads from R comps extra grip in corners and the general extra stress of track. Could almost be an annual thing with plenty of track work.

The GTP cars used to change them during the course of just one race meet.

Re saving dollars I know you can buy the replacement bearing kits from sources other than subaru ( bearing suppliers) and save a heap of bucks.