How often do you check tracking force?

@billstevenson  Thank you for the details. I run a Shibata stylus on my primary turntable. In the garage it is the original that came with the Pioneer which is where I want to start with inspections. My microscope is an antique, but the eyepieces are all new. My depth of field is okay at lower powers, but pretty tight as I crank up the power. https://www.facebook.com/share/p/16m754VXHU/  

It is fun to use and perhaps this will be the first time I use it for serious work. My Shibata has about 300 hours on it with every record always cleaned prior to playing. Some not so great as it was before I had an ultrasonic cleaner, but at least with a SpinClean. I got the Pioneer used so it is anyone's guess the condition, but then again, it is in the garage. 

@billstevenson "I have been checking stylus assemblies since working for a high end hi-fi shop in Seattle during my college years beginning in 1970 and I have not ever seen that happen."

That's because the assembly doesn't look noticeably worse, but it sure sounds that way. So what I'm saying that changes that occur with the cantilever will have a bigger negative impact on the cartridge's sonic performance that the stylus wear that may or may not occur within the same timeframe.

@thebrokenrecord Like I already wrote, in my experience stylus wear precedes cantilever failure.  When I check a stylus the set up is always refreshed.  For years I used ordinary test records to verify performance.  Last summer I invested in AnalogMagik, which is far more sophisticated.  So I am learning more all the time.  Perhaps I will discover what you have described in the near future.