Must be a bad batch. I'm not even sure how many winters I have on mine. It must be 4 or 5. Never lost a single stud, and all the studs are still in good shape.
That said, as much as I like riding these tires on ice, they are pretty much useless in snow or slush. If I was to ride much in those conditions, i'd go for a more aggressive tread like the Schwalbe Snow stud.