bearing endplay should be hand tight and no more. a water resistant grease is best to be used, and cool down your hubs before backing in the water. If you pop you caps and see the grease getting milky it is breaking down with the water. always carry a spare set of bearings with you. I get 5-7 years on a set of bearings and then I change them only cause I feel its time.
use American made bearings there are so many out there from China and they are junk first of all they have a problem with 52100 bearing steel and quality is poor that's why that almost what you see out there even from the trailer mfg. I have sold bearings for 35 plus years and have seen all kinds.