With an MM cartridge, a replacement stylus is typically 80% of the cost of the new cartridge itself. The costlier precision elements - stylus tip, cantilever, suspension - are all within the replacement itself. The rest is just the body, the induction coils, and the wiring to the four connectors, which don't cost much. Your call.
With a replacement stylus, it's advisable not to pull it out and push it back in (as some folks do, for cleaning) too often, as that might ultimately loosen the fit within the cartridge body. Any looseness or vibration would impact trackability of the stylus. For this reason, some manufacturers - like Clearaudio - make their MM carts with fixed, non-replaceable styli. Some vinyl addicts actually apply superglue to the outside of the sylus insert assembly to rule out even the slightest bit of vibration. Needless to add, they need a full new cartridge once the stylus lifespan runs out.
