there are a several types of ballchain. you have the nickle plated steel kind. the non-plated, stainless steel kind won't shed nickle plating flakes like you have experienced.
As for ballchain wearing out, yes it does. 13 gauge you should flip after 30 to 40 burns and then through out after another 30 or 40. 15 gauage will give you like 100 before you need to put the end that was by the wicks close to the handles and perhaps another 100 before you need to replace it. I've never seen 20 gauge break. And for what it is worth, percentage wise, I have seen normal link chain and swivel combinations break far more often than ballchain. Both chain types heat fatigue, but, as Valura said, you can tell when ballchain is getting ready to crap out on you, but not link chain.
Another benifit to ballchain besides it's non-tangly nature is that is doesn't have as much heat capacity - i.e. when you do get tangled in it, it will not burn you a fraction as much as hot link chain will because it has less metal and therefor holds less heat to burn you with.
Ballchain is the only thing I'll spin with, but you've got to keep on top of its maintanence, and avoid the plated type. Go to
ballchain.com to see all the varieties. They don't have a listing of types per se, but if you look under their "precut lengths" page, you'll see a variety of types. Basically there is brass, aluminum, and nickle or brass plated steel ballchain - none of which are good for fire poi (though the pure brass is ok for practice poi), and then there is the stainless steel variety - a little more expensive (at least in the local hardware store in Housotn), but the only kind appopriate for fire poi. Note that all the anodized/colored ballchain is either plated or aluminum, so don't be tempted by that like I was (Aluminum ball chain breaks really fast when you spin with it - even just glowsticks).
Hope that helps.
