I would suspect that improper replacement procedure is the culprit. I can't imagine a distorted knuckle or hub being the cause of bearing failure so quickly or repeatedly. I've worked with a lot of guys that change hub bearings with an air hammer and I'm here to tell ya that won't fly with Subarus. Most probable cause is the 'mechanic' (
) is pressing the new bearings in by applying pressure to the inner races thereby smashing the balls into the outer races. No matter what he/she is doing there is gross incompetency at work and the responsible party should be flogged. Now if they were failing after 500-1000 miles there may be a different problem. Hopefully they haven't done anything stupid (also hard to believe at this point) and caused further damage that will require more parts.
Good Luck at ya.
p.s. I've done a dozen or so SVX bearings in the past couple years here, without incident. Add in another 40-50 other Subarus in Denver - they're like the plague out there.