I get the question of "why am I blowing belts?" all the time. I normally say, "there are two things that blow belts, improper clutching and/or setup OR the problem is between the steering wheel and the Seat - Jumping and doing high speed whoops are fun to do in an X3 because the suspension is AWESOME but doing those things puts a lot of impact forces into your belt. Other things that can add abuse to you belts: power braking, burnouts, low to no belt engagement (rock crawling, trail loading, etc.), long hard pulls without cooling time.
The only belt I recommend for the price and quality is the Worlds Best Belts by GBoost.