What is the average lifespan of a phono cartridge?

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.

Dear @tbbromguard: Years ago Ortofon made a research about and they found out that after 500 hours any stylus tip showed signs of deterioration and this means that after those 500 hours that stylus tip it’s not tracking as is new: obviously.

In those times they said that when cartridge approach the 1K hours it’s time for re-tip.

Those informtion from Ortofon makes sense because if it’s true that at 500-K hours the stylus tip can has more hours to play with it’s true too thta’s is performing aginst listening enjoyment and against the LP grooves lifespan.

I know that through our ears and even after 1.5K-2K hours we just do not listen nothing wrong ( we are not aware of. ) but the damage exist in the stylus tip and will ruin those LP grooves.

Any one decides when to re-tip but maybe is time to think about again.

R.