Brass Life
The number of firings a cartridge case survives before necks split or the head loosens, a count that careful sizing and annealing can stretch considerably.
Brass life describes how many load-and-fire cycles a piece of brass endures before it cracks, splits at the neck, or fails near the head. Every firing expands the case to the chamber walls and every resizing squeezes it back, and that repeated working of the metal eventually causes fatigue. How long a case lasts depends on chamber pressure, how much the case is worked during sizing, and the quality of the brass itself.
Handloaders extend brass life by minimizing how far they push the shoulder back during full-length sizing and by annealing the necks to relieve work hardening. The failure that ends a case for good is often a split neck, which is harmless, or a case head separation, which is dangerous and means the case was overworked at the web. Tracking the number of firings in a data book is the simplest way to retire brass before it becomes a problem.