Cartridge new or used ?


How do I know if a cartridge is new or used and number of hours played ? 1- If it is bought from an individual or 2- Could it be that a HiFi store sells used or a "Demo" without anyone knowing it? 3- Is a cartridge that remains on the shelf of the store for 3 or 4 years, retains its same performance or its internal parts, can harden and lose their flexibility of reading? 4- Is it easy with a magnifying glass to see the wear of a cartridge, if so what would be the best magnification to use?
audiosens
I guess one exception could be where the stylus is user replaceable and the price is appropriate for such a contingency. Even then one takes one’s chances which is why I won’t do it again. I bought a used Pickering XSV3000 that came without a stylus. Bought the replacement stylus which was fine, but the cartridge has a noticeable channel imbalance which makes it unusable. So, between cartridge and new stylus, that was $200 down the drain. That put the stopper to future used-cartridge purchases.
No problem buying used. Preference is for them to actually be broken. Broken cantilever, missing stylus. Open coil would not interest me.

Off to the retipper once received.
Steve
I also bought a xsv3000 with completely worn out "E" stylus cw the very rare mounting pads.
Bought a replacement stylus and guess I was lucky as it sounded really good to my ears.
My ADC XLM mk2 and Sonus Bronze sound better but it was still a fair buy.
chakster,, there is a very big difference between a cartridge that has been well taken of by the original owner and one that has been worn out and possibly damaged by the prior owner. Obviously, as a cartridge is used, it wears, IOW..it is a wear item. The question is how it was treated in its past, not that it is wearing as we play it.IMO
I have some questions for all of those folks who buy used vintage cartridges, or used non replaceable stylus cartridges...
how do you know the condition of the diamond? Do you look online and get a generic picture that may or may not correspond with the stylus shape you are expecting to see, and are you able to actually view all of the facets of the diamond..on all sides, or are you doing something else? Using a high powered microscope? Are you able to determine the exact cut and angular correctness of the facets? 
Some other method to determine wear and condition? Do you have any idea as to the condition of the suspension and what that is supposed to perform like...or do you not care about this aspect that much, and assume all is as it was from the factory originally?