How often for micrometer calibration?

[Jimmy Olson]

While this thread deals with frequency for calibrating Micrometers, I'm curious about an old method used to check the flats on the Mic. In addition to using Jo-Blocks, we had to use calibrated pin gauges in three positions across the flats. To check for wear. Still done that way?

We use a relatively new invention for checking the flats called a light