Pull and inspect in the fall before you put up boat unless you fish year round. Every time before you grease jack up each wheel, check for any excess play by grabbing wheel and to shake it back and forth and lift up and down also get under trailer, spin tire and put your fingers on axle as close as you can to back of hub assy. If there are any bad sits in bearings you will feel it through the axle. Any of this seems out of the ordinary pull and inspect.