If you can keep them on, bearing buddies are the way to go. They are a valuable asset on something that sits around alot like a sled trailer, trailer bearings really need fresh clean grease especially the ones with the 8" rims because they are spinning so fast. I have noticed the newer trailers are coming with a "riflebored" spindle (like my 2000 US Cargo) where the grease travels all the way to just behind the rear bearing and pushes out to the front, the fitting is screwed into the end of the spindle and there is a grommet like "dustcap" that allows easy access to the fitting with no tools. After towing it 8000 miles last season, this past fall I pulled the bearings and such all out, and they looked great, I did not need to do it. Another suggestion is dont but 99 cent a tube grease, Buy someting like a good quality or synthetic that has good low and high temp performance because these wheels spin up to three times faster than the ones on your tow rig, it is no place to skimp. I would say it is a good idea to pull them apart and clean and repack every 2-3 seasons depending on how much you tow, and replace the seals at a minimum to keep out the crud. A side note, is I saw someone on a 4-lug trailer that had made a band that went under a lugnut, over the bearing buddy, and on to the opposing lugnut to keep his buddy on, there was an access hole for the grease gun in the middle......his dont fall off.