How do you tell your Cartridge needs replacing?

Fun off topic story that comes to mind since I’m currently sitting here without a phono cart waiting for new styli to be rebuilt at Soundsmith.

It seems different designs yield vastly different hours. After about 3000 hours of use I sent my Strain Gauge stylus to SoundSmith to be checked since it must clearly be worn after all this time.  Peter got back to me that it was not worn, and I used it for many years after that until it started sounding as mentioned above, spitty and sibilant.   Peter in one of his videos mentions a customer that played his strain gauge approximately 6000 hours before needing a new stylus.  
 

@emailists that is a fantastic story!  How is the stylus holding up so far?  I assume you must have at least another bunch of milage on it now some 3 years later!
I am really interested in this technology!

Hats Off to a Service that is willing to create a situation where its products are encouraged to be kept in their original condition for approaching 6000hrs is all usage has been favourable to achieve this.

In my world of 1000hrs as Gauge of usage life, that could be easy 5 returns for cleaning as a mid like fettle and 5 x Overhauls,   

Comparing what I would be outlaying vs the New Soundsmith Strain Gauge, my method would still leave quite a few spare coins in the coffers.