There is a multitude of situations that will effect thrust bearing life---assuming that the block, crank,bearings are properly prepared and assembled---everybody knows about throw out bearing non release, torque converter balooning---add in to that pilot bearing against input shaft splines, lack of clearance in complete drive line up to and including bad pinion bearings in the rear end pushing drive shaft forward, misaligned belts/pulleis on the front, a driver who rides the clutch pedal, sits at traffic lights with clutch engaged, etc, etc---------

As for the aftermarket saying that stock aluminum blocks are good for 800hp----that is nice of them, especially since they are trying to sell you one of theres!!!!!!!!!!!!