i have been using these mallets for 5 years now. the fact is, they need to be replaced at least every year, due to normal wear and tare. when these mallets get left in the rain the heads get waterlogged and loose their hardness, and even begin to fall apart, which would def. cause them to fall off. another thing might be the screw in the head of the mallet might be too small, sometimes they use the screws for the 1s or 2s for the 4s or 5s, so that could be it too. but overall that is a great mallet, one of the best, if not the best.
i disagree my line uses IP and we use these mallets and we've been using the same pairs for 3 years now.
the ones before that had been used for a LONG time...a good 5 years or more. we actually still have these, and they're in pretty good shape.
as to the heads coming off we haven't had this problem.
however i believe the screws ,as the person i quoted stated, might be loosening causing this problem