Cartridge life really only 3 years??

If it ain't broke - replace it right away; because it might break at any moment.

The body and suspension will be fine, the stylus is another matter. Different cartridges seem to have different life expectency, some quote 1000, up to 3000 hours, before the stylus is degraded enough, to damage your precious vinyl.
Then do'nt throw it away, get it retipped. there are a number of excellent companies providing retipping services. Many cartridges can be retipped more expensively by the manufacturer. Some reasonably cheaply, such as Benz Micro, some at near the cost of a new cartridge, such as koetsu, but with Koetsu, it is, effectively, a new cartridge

OUCH!!! Did he mention that you should buy them from the same dealer by any chance?? Looks like he's realy 'hungry' and perswaysive to pitch you a new cartridge instead of the one you have.

Hi Kk. I too am a long term hobbyist except I never abandoned vinyl. As suggested by other posts here, I believe three things can happen to a cartridge, other than accidental physical damage.

Stylus wear - The normal use expectancy for a diamond stylus is 1,000 hours, although some (example van den Hul) claim up to 3,000 hours. If you assume a generous average play time of 20 minutes for one side of an LP, that means 3,000 sides played. So long as the stylus tip and the records are kept reasonably clean, the age of the stylus should not be a consideration, rather it is the amount of use. Eyeball or low-powered magnification are not adequate to evaluate tip wear.

Suspension - I have no idea how many different suspension materials may be used by cartridge manufacturers but I do know the life expectancy can vary significantly. I've owned at least one cartridge (purchased new) where the suspension failed in less than three months. Another (that I still own) is now 20 years old and plays beautifully. The good news here is that mounting and playing a cartridge should indicate if the suspension has failed - the cartridge body may nearly (or actually) touch the record surface - or not. I don't believe failure is a slow, long-term occurrence. Rather, I think when it fails it happens rather quickly.

Alignment - If a used cartridge has not been mounted correctly or if anti-skate has been over compensated for an extender period of time, the cantilever/stylus may no longer be centered relative to the end of the cartridge body. This should be obvious from a visual inspection. This is critical for two reasons. Modern, narrow profile styli will not read the two channels correctly if not set perpendicular to the axis of the groove. And inside the cartridge body, the alignment between the magnet and coils will likely be incorrect if the cantilever is not centered.

So in my opinion, time in and of itself is not the determinant factor of when a cartridge should be repaired or replaced. But these three factors are.

BTW, I don't think I would take advice on analog playback from a dealer who does not sell analog components.

Yikes, my 34 year old Signet TK7SU lasted 31 years more than it should have.

It could go any decade now.

I'd better start looking.