1-2 a year. Usually ends up around 9-10 months between balls. Bought a Yeah Baby last August, a Big-R-Bang in November (?), which I then re-sold so it don't count. Before that, it was the previous September and January before that.
I figure I'm due, and the shop here has a Break on the wall for a pretty nice price. If it didn't overlap pretty square with my Yeah Baby, I'd be all over it.
SH