I have a bike which has wheels which I (sort of) built myself. I bought good quality hubs and rims, and had a friend who is a great wheelbuilder walk me through the process of building the wheels, using his tools and his spokes. He also calculated the spoke lengths for me. I ride the bike every day, and built the wheels 3 years ago. Every week or two I do minor maintenance, on the bike, lube and adjust, and check that the wheels are true, and I have patted myself on the back for how the wheels have remained perfectly true after 9500 miles. I have moved, and no longer have access to my friend, nor his tools.

Last night, on the way home from work, a spoke broke on the rear wheel - and I was curious as to why this might have happened. As soon as the spoke broke, the wheel was out of true (as would be expected), although the wheel seemed to be perfectly happy up until the break.

I'll be bringing the wheel into my LBS to have it repaired, and to have the hub serviced if it needs anything, so I'm not looking for advice on how to replace the spoke, rather, I am curious as to what might have caused it to pop after so many trouble free miles. Do I need to be worrying about the other 35 spokes on that wheel?