Originally Posted by
fietsbob
Preemptive Replacement of worn parts is encouraged for safety, as is having a thorough pre-ride check before starting a ride, on the bike..
Brake cable snapping at ball-tip is not likely a consequence of wear, but rather likely a consequence of manufacturing defect. There's unavoidable variability in manufacturing quality one has to always be ready for. Ball-tips snap from time to time.
Needless to say, "pre-ride checks" of such hidden parts are out of question (not even mentioning that such defects are for the most part undetectable). For the very same reasons "preemptive replacement" is as likely to replace a good part with a defective one.
Bicycles have redundant brakes for a reason. One has to always be ready for one of them failing without a warning.