What is the life span of a phono cartridge?

If your table and arm are set up correctly and your vinyl is properly cleaned, 5,000 hours of life are not uncommon for good quality (Class B and above) cartridges. Forget the magnifing glass at home...not enough magnification. I use a high power stereo microscope availiable at work for inspection. I also agree with Adle...you will more than likely swap out before wear out.
Regards

My silly response: It all depends on the cartridge. I sold a Linn LP12 with a Monster Alpha Genesis 1000 MC to a friend of mine years ago and he is still using it, I know that cartridge very well and it is still hanging on. The thing has got to be 8 years old by now. I also owned a Linn K-9 that only lasted me around 1000 hrs, I put it in a shelf for around 6 months and tried using it again only to find the suspension got hard (gave it to another friend so that she -yes a FEMALE audiophile- could re-tip it and use it).

I forgot the name of the writer but he was one of the 2-3 most famous names in the stereophile business, who wrote, "I have never as yet [in my audiophile career]wore out a cartridge" I think that the 1000 hours that the manufacturers give, is an arbitrary figure to cover abuse, dirty records and other unsavory conditions.

Isn't it the sylus that wears out?