Why would a break angle cause strings to die quickly? What about sweat, dirt, acidity, etc?
AHA! Great question!
First, my experience is related to a lot of basses over the years, but two in particular really brought this out. Both are Alembic Series I's; one the long scale, the other the short scale. Just due to the body configuration, Alembic had placed the tailpiece on the long scale about a mile back from the bridge. The strings had almost no break angle at all over the saddles and lasted darn near forever. The short scale had the tailpiece parked right at the bridge, which caused a huge break angle at the saddles. I used the same gauge strings on both instruments; and, in fact, the tension on the short scale was even lower by a bit. Nevertheless, the short scale eats strings for three squares a day. Kills them dead.
So, back to the original question, which I have also wondered about.
Indeed, scum buildup in the windings can probably damp the string harmonics a bit; but, I don't believe that is the primary effect. Its kind of like worrying about the mass of fleas on a dog.
The core of the strings is made of hardened steel. The likelihood is that damping primarily occurs at the witness point - the saddle. And, that is where the hardened core is bent at an angle, with greater bending for a higher break angle.
Well, my hypothesis has to do with what happens to the microstructure of the steel when it is bent. Steel is crystalline. It bends due to the motion of defects called dislocations in the crystals. The hardening process pins the dislocations in the crystals, which makes the material less lossy at the atomic scale. But, when you bend it, the dislocations become unpinned. The more bending, the more dislocations become mobile, the more lossy the steel becomes. It is a little similar to what happens when you bend a paper clip - gets easier and then finally breaks.
A similar example is that bells are carefully heat treated to tie up the dislocations - it makes them ring!
Anyhow, to prove this idea, you would have to get sections of the bent string core into a transmission electron microscope; a project I've often thought would be interesting, but which no one cares about enough to pay for. Such is our ROI oriented society!
Another thing - the boiling treatment: that's fine for removing the gunk in the windings, but if you wanted to re-pin the dislocations, you would have to heat the string to about 600C to 700C. That is what is required to get the atoms to move around. So, needless to say the 100C boiling treatment doesn't get close.
OK, that my Bill Nye explanation. For what it is worth.
The strings still go dead after a while.
Of course, there are other ways to design the bridge, but that is a whole different discussion.
