Here's my simple (& fairly foolproof) method to determine when a stylus reaches the end of its lifespan. It's one of several reasons why I only use cartridges with replaceable styli: - A new cartridge is always purchased with a spare stylus. - Both are run for around 50 hrs & the spare put away. - As the in-use stylus gradually degrades, the spare can be used as a listening reference to determine when another is needed. - When that happens, a new one is purchased, run for about 50 hrs & that then becomes the spare. - The worn one is discarded & the original ‘spare’ is used. It isn’t easy to do this with a moving coil without the cost of purchasing two cartridges & then only with arms with removable headshells. Properly cleaned vinyl stored in anti static sleeves, brushing records & styli after every play & always playing with the cover closed means I usually get well over 1000 hours before any noticeable changes.