Bungee's snapping actually aren't that bad, since usually only one thread snaps and you just lose your speed. Theoretically it could happen at the worse moment, but I've seen a couple break and it's never been a bid deal other than that it really sucks that you don't have a bungee any more and you're at a spot where you need a bungee. Pretty much all bungees develop cracks in the rubber, if they grow big enough they will eventually break a thread though and become useless.
I'd say send it until it breaks. That's pretty much all you can do with a bungee anyway.
