Blazer ball joint woes

I have a 2001 2dr 4wd 5 speed Blazer that is driven on almost billiard table smooth streets and had an oil change with lube every 3,000 miles. At about 55,000 miles when the steering was cranked from almost lock to lock, like when backing out of a parking space, a knocking sound could be heard. I had read a service bulletin on the sound saying it was due to ball joint wear and took it into the dealer and was told the lower ball joints were worn. They were replaced under warranty and the tech who worked on it said most Blazers don't make it to 50,000 miles without needing a replacement and he commented on how well kept and tight my Blazer was. I can't fathom lowers wearing out that fast under those conditions so there has to be one of two things wrong; a design flaw, or the bazaar front alignment settings they leave the factory with. I read that the front alignment is set up differently for four wheel drive to prevent excessive over steer when "Ma and Pa average without a clue" put it in 4wd in the snow and then proceed to drive it like a Honda Civic on a sunny day does anyone know if that is true?. Also I noticed that from new the steering was very numb off center, could this also be a characteristic of the alignment setting? I have also read about Toyota pickups with 4wd eating lower joints. The parts can't be from the same supplier so again I think it possibly points to "safe" alignment settings. I noticed that the Toyotas and the Blazers had one thing in common. When viewed from the front, the front wheels of brand new Toyota 4wd pickups and Blazers were dramatically off from perpendicular to the street with a decided outward tilt on the top. I understand the unequal length control arms and excessively high ride height of a new vehicle before the springs or torsion bars wear in could cause the wheels to be tilted slightly but on these two vehicles the tilt was very pronounced indeed and with the shorter arms on the top shoulden't the higher than normal ride hight have them tilting the other way? Could the alignment be the reason for the wear and if so what would be a more sane alignment setting for those of us driving Blazers who know what we are driving? Please help warranty ends in three months.:(