I've gone through spare balls like i go through the sushi buffet, fast. Spare balls don't last in my hands and I don't throw hard like Max Rob. The spare tire seemed to hold up well, but I retired that ball in dedication to a friend who used my ball during leagues one year when he battled cancer. (went from rolling 16 mph to 12 mph)
Anyway, Storm, C300, Ebo, and bruns spare balls don't hold up well for me. My roll clips the finger/thumb holes which crack over time.