I was called to replace a string in a church the other day, and found myself about to the end of my coil of #17 wire. I had more than enough to do the job, but all the wire I attempted to put on broke at the becket immediately on starting the pin winding. Of course, I purchased the wire some time ago....maybe even when I started in this biz 25 years ago. Question is... does music wire have a shelf life? Has anyone else experience this?

It is possible that you got a batch that was improperly tempered. I had that happen once.

Its possible that this stuff has had it by now. Even though it was on a coil, the string has not been under any tension for 25 years. It was also wound around itself and being subjected to changes in temperature & humidity over the years. I read recently in a technical book on piano acoustics that strings do have a 25-30 year life span but many old pianos still have original strings. Perhaps they have survived because they have been under tension. I'll try to look up more on this issue but for now I suggest you ditch your old string supply and get a few new coils with brakes for your stringing kit.

I don't believe unstressed wire has a shell life as long as it isn't rusty and hasn't suffered some other damage. To assume otherwise, I would think you'd have to postulate that the metal's grain structure changed over time. I don't think that happens. We need a metallurgist to answer the question definitively.