I use an Era III all the time and a few others. They all still seem to work just fine. Perhaps it was recommended to change them out often back when they were plentiful, but now they aren’t. Perhaps the advice to change them out a lot is kind of like the 3,000 mile motor oil change recommendation—liberally dusted with OCD good sense and overkill?
I can’t say.
In any case, the only one that I’m aware of that has a stylus wear test is the CBS STR-100, and it’s indirect. In any case, if you can only hear up to 12kHz in your right ear and 14k in your left ear, which the CBS STR-100 gracefully demonstrates to me, it’s of limited value for checking a cartridge up to 20kHz if using one’s ears. You’d need something graphical to accompany it. I can test up to 14kHz with both channels by turning my headphones around, though!!!