Perhaps the "never" was a bit rash ! but the original boxes lasted 12 years
My gearboxes a re Leroy Somers.
The boom gearbox failed as the oil had leaked out (before I owned the boat) and the gears just gave up.
The main gearbox was replaced as the housing was actually falling apart.
The gearboxes are not that diffcult to take off and take apart, unless it hasn't been done for a while.
I still don't see the point of squirting grease into them.