Centrifugal force throws grease out. No wonder we're always replacing bearings. Nine, before you leave take a small floor jack and listen to each bearing before greasing. Put the jack in the vehicle along with the trailer spare and lug wrench. Ten, when you wash the boat, completely rinse the inside and outside of the trailer and the rear of the tow.
Trailers rust out from the inside.
All this effort adds to your peace of mind while towing and the chances of a trouble-free trip.