I've seen a fair few shrouds break, but all that I can remember are on boats that are sat in the boat-park for long periods with the rigging left slack and the mast jerking about in the wind.
Saying that, I am a believer that shrouds should be changed ever 2 seasons. I have a workshop full of old ones.
It always amazes me when someone spots a shroud or trap wire fraying at the swage, they then go and just replace that one alone! Surely if one has come the the end of its lifespan, they all need changing.
I am also surprised when people only replace one broken J+H handle too! I like to relax a bit on the wire!