Are 500 hours too many for a used hi-end cartridge?

I have been looking for good used mc cartridges on Audiogon in the $800-1000 price range. Most cartridges at this price advertise 20 to 200 hours. A few questions:
1. Are the advertised hours believable, since turntables do not have elapsed time meters?
2. Is cartridge age more important than playing time?
3. Is 500 hrs too high for the purchase of a used mc cartridge?

Thanks again for your comments. The posters seem divided on pro-used cartridges vs anti-used. Taking all your thoughts into consideration, for me, at this price range, I’m probably going new with an AT ART9, to minimize variables. Also to have a local human to deal with if there are problems.
Happy listening.
PS I may have a slightly used Hana EL for sale if this works out (somewhere between 50 and 200 hours of use I estimate). Or maybe I’ll just keep it.
@cakids You don’t need a local vendor, you need the AT’s distributor support so you can give your cartridge (when it’s worn) to the distributor of the Audio-Technica and he can ship it back to Japan. Audio-Technica do not repair cartridges, they do not re-tip cartridges, you will get a brand new cartridges with their exchange program (for about 60% of retail cost), only if you have valid serial number and if it was purchased from official AT dealer/distributor in your region. Don’t buy grey market samples, they will never service them.

Forget about re-tippers, this is not the same.

Stay with Audio-Technica to get full support from their distributor, this is much better, believe me.

When one ART9 is worn they will give you another if you send yours back, new cartridge with new suspension is much better than third party re-tip. Or maybe you could even upgrade to ART-1000 one day, if they have upgrade program. Only official AT distributor can help you with it. 
I think enough people have answered to confuse you on buying used or new. I want to share, instead, how I keep track of my cartridge hours. I once purchased a box of hand tally counters (the sort that you see where places are trying to count how many people have entered.) Maybe 12 bucks for a pack of 6 on Amazon when I acquired them. 

 With a label machine, I indicate the cartridge and the date I acquired it. Then, every time I play an album side on that cartridge, I click the appropriate tally counter once. This may sound onerous, but between using a carbon fiber brush, some blue tak on the stylus, and pressing the tally counter probably requires 20 seconds maximum. More like 10. It’s a worthwhile routine to develop and keeps needle and vinyl in excellent condition. (This assumes you first cleaned your vinyl properly on acquisition). It’s just like brushing your teeth—proper habits preserve health and money. 
I then divide by three to give an estimate of the hours, knowing that this will yield a slightly higher number since few albums sides are a full 20 minutes.

Then you are empowered to decide how many hours a given stylus should last, or when you need to scope the stylus. Simple. 
The only used cart I ever bought was when  starting to assemble my first high end system and looking to save money, being fresh out of college.

 It was a Spectral cart (anyone remember those) that i bought on Audiomart newsletter and the entire assembly was tilted. The seller didn’t want to return the money and I think settled on refunding half after I got the owner of audiomart involved. My bank had told me incorrectly that a bank check (or certified, I forget) could be cancelled. I confirmed it several times and was always told yes. When I tried to cancel the check, of course it wasn’t- but my bank paid off anyway since I had people’s names that told me the wrong info.

never bought a used phono cart again, but also bought many used high end gear and never had an issue other than that once.

incidentally my strain gauge cart has many thousands of hours and now I want to have it checked .  Sounsmith was quoted saying a strain gauge owner put 6000 hours on listening to vinyl all day long, and after sending back to Peter to look at under a microscope, the stylus still was not worn out.  Sounds crazy, but Tam henderson from reference recordings claims he plays test lacquers with the cart and they don’t wear out! 
1. no, most quoted low hours tend to be vastly understated, reality without documented proof is a guess at best,
2. yes, cartridge components deteriorate over time, with or without use,
3. yes, see 1.