Case life will vary from one firing to a point where you realize they are never going to expire. At that time, just give them to a needy shooter so you can treat yourself to a new batch. Brass life will vary with the pressures and degree of movement or stress to which the case is subjected. A .38 Super case that must make a major power factor may be finished after one firing. Yet a low pressure 45 ACP case may last until the cows come home if not overly crimped or belled too far.
How many firings can be expected from a case?
Sierra Bullets > FAQs > How many firings can be expected from a case?