How do you know when to replace the stylist?

And can you replace the stylist or do you have to replace the whole cartridge?

Thanks in advance :)

I replaced my stylist after the last bad haircut. :)

Generally, only a MM cart has a stylus that can be replaced, although some MC carts can be retipped.
When your stylist has highlights and earings in both ears.
When he offers to style your Body hair!!!!
I would never let a stylist anywhere near my cartridge.
Sorry Stylus...Bummer can't edit original post. :o

Who can retip a MC cartridge and how do you know when.
Check with the dealer(s) of the cartridges that interest you. They can point you in the direction of re-tippers, and they can tell you how many hours to expect out of the stylus.

Benz Micro has a trade-in program. Soundsmith re-tips Denon carts, I believe.
Thanks Tvad...VERY Helpful
1. When you have enough $$$ in bank account.
2. When you are no longer satisfied with the sound produced by the current cartridge.
3. When hear your friend (or anybody) bragging about a new cartridge and how good it is.
4. After finding out the needle is worn out (inspecting with at least 30x magnifier glass or microscope).
5. When you have just found out a real deal going on ebay (or agon) and would not want to miss the deal.

Actually, those were most of the reasons why I replaced the cartridge/needle. 5-3-1-2-4 is the order (the most frequent/compelling to the least frequent/compelling reason) that have occurred to me. I guess I have bought about 15 cartridges over the last 10 years, from Grado ($30) to Clearaudio ($250).
"When [you] hear your friend (or anybody) bragging about a new cartridge and how good it is."

Hee-hee...My system can beat up your system :b
Usually it starts out with a slight degradation in cymbals, or some sybilance in sounds, then outright distortion with various types of music. It will appear at first as if the needle is dirty and trying to clean it will not change the sound. Try to imagine your needle full of sludge and worn down trying to play a groove,,,that will sound bad.
I second what audioquest 4life says. I am in the process of replacing my current cartridge. I started loosing detail in the high frequencies and certain passages started sounding more sibilant, and some music would just totally distort to where I couldn't listen. Basically the cartridge couldn't track well any more. It sounded like bad inner groove distortion.
At one time: Every serious audio salon(not going back to the "stylist" thing- honest) had a microscope which which to inspect your stylus. I'm certain(if you live near a metropolitan area) you could still find one. Really- any decent microscope would do. Just look for wear at the points of contact with the groove walls. Here are a couple stylus retipper tips:( ( If you have a cartridge that's honestly worth the effort Van den Hul is the bomb!! Plug, "stylus retipping" in your searchbar for more options.
OH- On the Van den Hul site: You have to click on "phono cartridges"(left of page), then "extra services" at the bottom of the cartridge list.