Bearing Buddies and the like attempt to push grease into the outer bearing when the grease is applied. Other than a small spring, I don't see how there's any real pressure that will do anything except keeping it on the back side of the outer bearing. They don't do anything for the inner bearing or grease between the bearings. I've greased the one's on my brother's boat trailer and those springs are weak. Grease usually just oozes around the edges once the spring is compacted. If it's going past the retaining spring it can't be going the other way with much force. I believe it's about as effective as filling the dust cap with grease.
I have a Ranger trailer where the spindle axle is hollow, grease is forced through the spindle end (pretty good force), between the bearings, where openings in the inner axle will allow it to ooze out around both bearings once the area between them is filled. This pushes out the old grease with the new grease. Still, I repack them each year and replace the inner seals if they are leaking.
There is the concern with using this type of spindle on travel trailers, the grease can be forced past the inner grease seal and onto the brakes. The same with Bearing Buddies.
Your AS trailer shouldn't ever be immersed but with a heavy rain, puddles might be deep enough to allow water to enter if your seals are bad. Use a good waterproof grease, like they use for boat trailers, and check your inner seals. Repack them if you see grease leaking onto the wheel and tire from a bad seal.
Avoid boat ramps