I had bearing buddies on a new to me camper. I did some reading, decided I didn't like them, so I went to pull them off. They were pumped up nicely, but, all the grease was on the outside bearing. They had not gotten through to the inner. Maybe there was an air pocket and the grease would eventually work over, but in the end, since it wasn't going into water I removed altogether.
My latest acquisition has a zerk in the axle, in the center, the nut and bearing go over it. It's an E-Z-Lube or similar. Not trusting it, I pulled apart the bearings once I got the trailer home. This axle is set up to direct the grease through the spindle and to the bearing surfaces. Cool. I'm not sure how much I would trust it, maybe hit it with a few pumps once every 1,000 miles or somesuch--but I think pulling apart, inspecting, and packing in some fresh grease is always a good idea. I just don't know what is a good interval for it (yeah you can read your owners manual but who wants to do that?).