I would be keen to know too, been 30 months or so with maybe a handful of spin downs in total, wet cloth wipe now and then. Still humming as if out of the box.
Kickr '18 here. Other than wiping down, I have removed the cassette and hub to give a thorough cleaning and greased as per @GPLama’s vid on making it a bit more silent.
Clicky freehub generally means the pawls are engaging snappily. This is good in that if they are slow to engage and aren’t fully engaged when torque is applied, the pawls or ratchet ring can get damaged. (Low temps can slow pawl engagement.) Pedaling trainers when standing can sometime get clunky, which exposes the pawls to disengaging and reengaging at high torque against the inertia of the flywheel, so it’s good to have snappy pawl engagement. Some designs are louder than others, and it’s usually best to use the freehub lube specified by the manufacturer. FWIW, I use 90 weight gear oil on my trainer’s pawls.