I can't remember the last time I broke a string while playing.
However, I have a nylon string acoustic that will occasionally break a string while it's in its case. The D string likes to break on its own, no playing required. Weird, I never could figure out what the deal was with that. Although I don't think it's happened since I started using Oasis soundhole humidifiers a couple of years ago. Could the wood really move enough to break a string when it's dehydrated?