I've found Sm57s to be very, very reliable, and very durable. However, there's a DIRTH of fakes out there, and they're utter crap. They work, but they explode the instant a drummer hits them, among other things.
I've had at least a dozen of them over the years, and about 1/2 of them broke or exploded or whatever. Every single one of the broken and exploded ones were fakes, and I only learned about this earlier this year when I started reading up about fake SM 57s. I'm not alone in this. When I found out about it, I called a couple of friends with studios. It turns out they had several fakes without ever knowing it, too.
Actually, one guy with the studio complained about having a mic explode on him. It happened that I read a thread on another unrelated forum about it, and started checking the exploded ones that I had (I'm a saver, and tend not to even throw out broken crap.) I was shocked and pissed. I gave him a call, and sure enough, his bad mics were fakes. I have another friend in the Bay Area that runs a nice, professional studio, and told him about it. He had a few in his arsenal, too, though they weren't busted (yet).
I made the mistake of buying most of them used off of Craigslist. Bad move. There's a ton of fakes out there, and there's even some that have made their way into some music shops.
Walter - do you still your busted mics, or are you sure of where you got them (i.e. did you personally buy them at a reputable place, not just get them from a buddy)? Check around on the internet, and, unfortunately, you might have been given the shaft.