ProfessorM,
If you are having trouble with your wheel bearings, start using Lubrication Engineers grease. It can not mix with water. Check out there website www.le-inc.com there is probably a distributor in your area. If not I have lots of it
I pull my wheels every fall, take all bearings out was with degrease and repack, reinstall. I use marine grease and have had the same bearings for 7 years on the old trailer, and 4 years on the new trailer.