Hate to be contrary here, but I think just taking track of hours used is no indicator of wear at all...none! Some cartridges can be damaged or worn with very few hours on the clock...depending on how clean the LP is and what shape the stylus is to begin with! Others can have very long lives with no visible wear at all....visible to the naked eye that is.
Playing a test record is also no indicator....what kind of aural memory do you guys think we have, LOL!
Paraneer, do you have any idea as to what the diamond shape is supposed to look like...exactly look like, under the microscope or even worse...the loop. I know I don’t! By the time something has failed with the diamond shape, you have done immeasurable damage to your records.....hmmm. Do you hear this damage onset on the first play, the next play or the ??? play....my question.