Think about a guitar that can convert from fretted situation to fretless.. It’s very easy to do that when you are playing the instrument. It uses a rounded facet in fretted mode and a flat facet in fretless mode. The principle behind the mechanism is a rotating fret.
Let’s see some videos how that frets work..
Convertible (Fretted/Fretless) Bass Guitar Demo
Convertible 6 String Electric Guitar
According to MIKEY GUITAR (the manufacturer of these instruments) These instruments do not need for maintenance or adjustment. the meterials used for making the frets are polished stainless steel for long life. The frets require no lubrication.
They have also had a stress test to prove the durability of the mechanism. The mechanism was hooked up between two solenoids and driven back and forth. A counter kept track of the cycles. The “clack clack” sound of the solenoids drove everyone nuts but, over the course of 8 weeks, the mechanism was cycled 1,000,581 times. That’s equal if you switch 20 time back and forth a day for about 137 years. there is no signs of wear in this observation.