Originally Posted by
mrrabbit
..eventually given time and depending upon the quality of the nipple - long or short - nipple barrels will start to crack and separate from the head of the nipples. Head gets lefts on rim seat - barrel slides up and down the spoke like a cheap wheel decoration.
Er, what?
The only part of the nipple that would be free to slide on the spoke is the unthreaded part closest to the hub (the first 4 mm or so), and as it's unthreaded it can't carry a load. And if it can't carry a load it can't fatigue.
I've had the occasional nipple snap, but usually in connection with a crash. And on those occasions the "barrel" of the nipple has always remain firmly threaded onto the spoke end.