I know people using lemon oil every two weeks on their fretboards for 20+ years. This is a myth. I sometimes think people start these myths just to fuck with people. Alternately, it could be techs. What techs do is not magic. If you are mechanically inclined, you can pick it up extremely fast. It is measurment and adjustment. Soldering, lubricating. If you have expendable income and a good tech, fuck it. However, a setup is very personal, so I have had a tech do it when i was lazy, and the guitar came back with way too low of an action. Everyone brags about a low action, so techs naturally just go to this. But if you are a heavy player, this is not the way. So no tech will set things up the way you can, simply because they do not play the guuitar for you.