How can lug nuts come loose?

Was on my wife's 2006 dodge caravan with aluminum. Put on almost two months ago, check them every three weeks. Van's 4 years old and the rims are factory. Planning to see my buddy who has his own shop, might just change the studs and lug nuts to new. Dealer mechanics and their air guns like to make them as tight as possible and over time I think the studs might be stretched. I remove them with a air gun, but put them on with a torque wrench. Dealer changed my snows to summer last. Before that never had a problem. The dealer has also broken a couple of studs. Have since learned mopar uses crapy wheel studs on the caravans and is a common problem. Only the front driver side and it was a little low on air. Up here guys like to put blocks under the frame of the car and let the air out of the tires and then just unbolt them....picking up some lock nuts aswell...better to be safe than sorry...vehicals just aren't made the same anymore