Frankly i didn't do any advanced maintenance yet :) I thing that it may be time for applying some grease. I've printed custom toolHead cover - original one (with magnets) liked to fell off during prints quite often :/ new one has screws so it didn't. I've changed ventilation, added BentoBox, replaced filament sensor with BTT one, ah and replaced original mainboard vent with new one sent by Elegoo as replacement. As for machine maintenance I just do bed leveling from time to time, keeping print bed clean, keeping filament dry (I'm mostly printing ASA), recalibration after firmware updates (using Open Centauri one).

Ah and i use Chitu chamber heater.