OK, now we know that the bearings and probably the brakes were never serviced well. Bearings can last the life of a trailer or begin to fail immediately if they were made poorly. I have had cheap Chinese bearings that were defective and could have failed at any time. My advice is to replace cheap bearings with a brand such as Timken, then forget about the grease fitting and service the bearings when you do your annual brake inspection.
I would not replace brakes that have plenty of lining remaining and magnets that are not excessively worn. Grease soaked linings should be replaced. Look at the armature where the magnets ride and use that to make a judgment whether the drums or magnets should be resurfaced or replaced. Know that few can resurface armatures properly.
