srlsy, I'm sorry to hear of your woes. It does sound like your bike shop is awful, its not hard to sinch a cog down and snug up a lockring.

The 06 hubs seem to be (based on incidental reports on SS/FG) a poor lot, but I doubt they'd strip if the locking and cog are properly installed (and maintained).

Its probably worth getting a lockring tool (or borrowing one) for when you (or LBS) install a new cog as theres always the chance it will tighten a little bit further during riding; a Hozan lockring wrench is around 20 bucks.