I have two answers. On two turntables, both with fixed head shells, once set up the variables do not change. I re-verify the settings, but nothing ever changes on either one between stylus examination under microscope. I do that annually on one and semi-annually on the other based on usage. The third turntable has a removable head shell and cartridge changes are frequent. On that one, like Elliott, I check and adjust frequently all parameters. I use analogMagik to set up and adjust all parameters and examine all styluii using a Wild-Herrbrugg microscope either an M3 or an M5.