How do tell when my stylus is too much worn?

I have had my MC cartridge for about 5 years. I haven't kept a proper log but I would guess about 7-800 hrs. How can I tell BY LISTENING that it is worn enough to replace or retip? Does it get edgy or shrill or....?
I suspect that the change would be so gradual that it might be hard to tell, as the ear slowly accomodates.
Of course I should remove the cartridge and view under a microscope but un mounting and remounting is a perilous business that I would like to avoid.