I've used some cartridges for many many years maybe well over 2000 hrs. Sent one to SoundSmith who told me after looking at it there still was life in it. So many factors can come into play, are you tracking at the right force? Keeping your records clean? Etc
Nagaoka MP 300 Cartridge
I was thinking I should know more about the average lifespan in hours of this cartridge so I can start thinking about a replacement. If you can help please let me know.