In my experience, classical guitar strings have a life expectancy of between 1 second and 100 years. They can snap for no apparent reason; they can fray at the saddle or nut; they can come unwound. They can do any or all of these things when being played vigorously, when they are over-tightened, or just when lying quietly in their case.
Because of this all strings are sold without any warranty whatsoever as to their life expectancy.
If you pay more you cannot expect any difference in this regard – the life of an expensive string is as likely to be short, or long, as that of a cheaper one. Certain makes however appear more prone to breakage than others – hand-made strings do appear to be more vulnerable than computer-controlled factory made strings.
While the actual time of breakage is unpredictable, it is a fact that the more you play, the faster the strings wear. You will notice this first on the wound, bass, strings with discolouration spreading out typically around the area over the lower frets. As soon as this is really noticeable, it is likely that your strings have lost the best of their tonal qualities; it is also a sign that the day of breakage is coming nearer.
There are more subtle problems – particularly intonation issues. Some strings are not regular over their length in terms of width or density. Strings with these defects give intonation problems. I think if you get such a problem (and you think it is worth the trouble) then you may want to complain. I have done so myself when I had a batch of strings all with the same problem.
- If you are a performer then have several sets of spare strings in your case at all times
- Protect the soundboard behind the bridge when restringing as this is the most common time when strings break – and they can do a lot of damage if they snap back onto the soundboard; use a proprietary product or a DIY solution).
- Examine nut, frets and saddle frequently for roughness which can increase fraying or rapid breaking
- if you can feel roughness, then polish first with fine grade sandpaper.
- even if you cannot feel roughness it is worthwhile polishing the top of the saddle with very fine grade sandpaper
- polish the grooves of the nut with very fine grade sandpaper folded into a V shape to fit into the grooves.
- Tune strings 1 semi-tone flat for the first 24 hours (and keep them there perhaps if you are using period strings)
- Clean your strings regularly (after each session) using a cloth or a proprietary product
- Finally, confirm that your guitar is of standard scale length – if the scale is longer than 650mm and you are fitting “high tension” or “extra high tension” strings you may be stretching them beyond their design limits.
Another problem with strings is that they lose their tone. This afflicts wound bass strings more than unwound nylon or composite trebles. This starts to occur within hours and continues rapidly for a while until there is not much tone left. Many professionals would say they are finished by the end of the concert for which they were fitted; many amateurs keep them on for years. So there is no point of consensus as to how long this process takes.
Finally, and this point is particularly for players more used to steel strings, nylon strings (and silver wound strings with nylon cores as fitted to classical guitars) never really finish stretching. This is the reason why you always have to keep tuning the classical guitar because the strings never reach the point of stabilty that steel strings do after a few hours or days. By the time a nylon string has finished stretching it has probably lost all its tone (this is particularly true of the wound bass strings).