How old is your cartridge?

It is very possible for some cartridges to last seemingly forever while others can have a worn stylus in as few as 800 hours. I've seen both.
At the end of the day, diamonds do have different hardness. A user won't know what they have 'til they know.

Good point Boothryod! At some point, either late 80’s or early 90’s, I had a cartridge when part of the Diamond split off. And it was relatively new too- 

Dear @zavato  :  Yes, rubber deteriorates over time. Now, not all cartridges were designed with the same kind of overall suspension set/kit, suspension is not only about that " rubber ", even Ortofon has a trade mark on the kind of suspension they use.

So some cartridge suspensions are more suceptible to degrading over time and something important about is how carefully the cartridge owners are with their samples.

If you ownonly  one cartridge and you used it 4-5 days every week for 3 hours each time then the stylus tip goes out of play after around 1,500-2,000 hours so you have to send to a re-tipper whom not only will change the stylus tip but he makes a check up in the cartridge suspension and if need it he changes dampers and other suspension parts, repeat if the cartridge need it.
So in this way your cartridge can " live " almost for ever because in normal playing condition the cartridge motor just does not deteriorates as could be the suspension.

Allaerts gives at elast 20+ years of cartridge live with around 5K hours in its stylus tip, this comes from his site:

"  and has an expected life of five thousand playing hours. "

I own120-130 vintage and today cartridges that more or less are in rotation so its playing hours of each one are in true lower that we can imagine but and especially with vintage MM/MI and even that be NOS no one can gives you an absolute warranty that that cartridge will play well not for 1K hours but not even for 100 hours and that's why no seller gives you warranty about. Some of those cartridges after less than 50 hours falls down. I had that type of experiences with used and NOS vintage cartridge, normally MM/MI ones I can't remember rigth now a LOMC cartridge where I experienced the same and I own several LOMC ones just because are superior quality performers than the MM/MI designs.

In the long MM/MI thread J.Carr was rigth when posted there about that LOMC superiority. In those times I was in disagreement with him, from some years now not any more.

Regards and enjoy the MUSIC NOT DISTORTIONS,
R.

Current cartridges under my possession:
SPU Gold reference - almost 10 years
SPU Silver meister MK ii - 3 years
Ortofon SPU mono - 4 years
Ortofon SL15e -?? needs to be retipped
Ortofon SL20Q - ?? needs to be retipped
Ortofon MC100 -?? hardly used since it is inferior to others
Ortofon MC20 super - 1 month (retipped newly)
Denon DL103r - 5 years
Denon DL303 - ?? still sounds good
Denon DL102 - 7 years, not used much
Audio Technica AT150mlx -- 2 years (second replacement of stylus)

Three arms in use. One arm (Ortofon RMG 309) needs to be fixed, and need to find out where to send it to get it fixed. One arm coming soon. So will have 5 arms in action some time this year.

There is a difference between the age of a cartridge and the age of the stylus tip. 

A New Old Stock cartridge can be 40 y.o. (unused), and your stylus can be used only for 2000 hrs max (with the best possible stylus profile).