What is the average lifespan of a phono cartridge?

@chakster
that is exactly right. I have a friend who has destroyed numerous valuable records that he owns while playing old SPU’s and other London’s etc., Poor guy didn’t realize that the stylus was worn out, even though the suspension seemed to be ok.The elliptical and conical styluses were so worn that after just one play the damage was done. He only recently discovered what he had done by listening to a new Clearaudio Goldfinger ---and then hearing the damage! Shame that somebody had strongly recommended the older cartridges and he followed their advice---blindly.

Agree with @chakster .  Different stylus profiles have different lifespans.  Also, the construction quality of a stylus can impact lifespan (crystal structure alignment).  The various line contact styles / profiles listed by chaster have a larger contact surface area that spreads the load over the stylus.  This increases lifespan.  A conical cartridge profile has a very small contact area, actually just a point of contact.  These wear very quickly.  

BUT NOT TO FEAR!!!   

Just because some damage might be done to a record due to a worn conical stylus does NOT mean that your records are totally ruined and unplayable.  A new cartridge using a very small line contact stylus or a cart rebuilt by Soundsmith or others using a very small line contact stylus will be tracing the record groove in a different area, typically tracking MUCH DEEPER in the groove.  This area may not have been damaged.  May not have ever even been touched by a stylus.

I recently had Soundsmith rebuild a cartridge using one of their very small line contact stylus / boron cantilever combinations.  When playing some of my collection that was damaged in the early 80s by a worn Shure conical stylus came out clean sounding and like new.  No audible damage or distortion.  The stylus was obviously tracking a "virgin" part of the groove.

@bpoletti 

I don't agree. Once the groove is damaged, that is going to severely impact the SQ of the record, period. Just because your stylus is tracking a slightly different section of the groove...which may or may not be true, doesn't mean to say that the stylus won't be also tracking the damaged section...and that damage is usually pretty significant...and easily heard. YMMV.

@daveyf you do know that the majority of
stylii are inferior conical/spherical contact? Even a lowly bonded elliptical stylus can track virgin vinyl that the dreaded conical/spherical stylus has not spoiled. Then microline styli can go even further. Don’t give up so easily!!

It is possible to trace a different part of the groove and mitigate at least some groove damage; I've heard this myself.  When a record is damaged by mis-tracking or a bad stylus, chunks of vinyl are removed so that the wall becomes pitted, it is possible to avoid these pits by contacting the groove above and below that area.  When a record is played, the stylus deforms the groove slightly, but because vinyl is highly elastic, it snaps back to its original shape.  The pits will affect how the groove deforms, so even though a different stylus might not be tracing the pits, the absence of vinyl will affect how the groove deforms, so, in that sense, the pitting cannot be totally avoided unless one uses a system like the ELP laser table.  I saw a demonstration of that table where a severely worn record was played with the laser focused at different groove depth--when the laser avoided the damaged part of the groove the record sounded like it was new.