I have broken spokes, but in three different scenarios - (1) a wheel built by someone who is respected as a wheel builder but I always thought built with too little tension for big riders, and on wheels that I have built including higher tension than I generally see from other builders has pretty much ended my broken spoke days, except for when (2) I had a junk bike taken from a dumpster, and all I did was pump the tires and oil the chain; condition and build quality of wheels unknown. (3) And, a bent derailleur hanger allowed my chain to get behind the cassette and chew up the spokes next to the elbow on a wheel I built for my mtb - at first I was heartbroken, thinking my wheel build was not as good as I thought, then remembered the months previous chain-behind-the-cassette problem and lo! found the spoke was broken right in the middle of the biggest gouge.

But my current wheels, built ~10 years ago have many thousands of kms on them, some on pavement, but many on rough gravel and dirt roads and trails, have not broken a spoke. Two frames have reached the end of their lives (cracked) while using these wheels, but I slapped them onto the most recent replacement frame and have not had a problem yet.