I think the rule of thumb is around 1,500 hours. Van den Hull advertised some of his cartridges (at least the Frog) was good for 3,000 or more (twice the average). Mine had well over 2,000 when I sold the turntable… it sounded perfect.
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.