I am in the minority here, but I remove the grease nipple and install Bearing Buddies on them, and it works great.
You do NOT have to add a ton of pressure to them and blow out your rear seal. Just a single pump, normally, just enough to make sure it remains full of grease. I have a trailer with unknown many miles on it with this system, and zero issues. Never rebuilt, and I'd take it to Florida today, if I wanted to with no concerns.
My all-time favorite hub system, is a dead tie right now. I have a boat with an oil-filled hub with a clear window. I've got to say, it's pretty nice. You never have to do anything. At least I haven't yet. I need to google to see the process to change the oil, but that may be awhile before needed.
Besides that, my long-time favorite has been the E-Z Loader, Flow-Thru hub system on their torsion suspension axles. This is one with a relief valve through the back of the axle. You grease normally, but a couple of times, a year, you pump grease until all the nasty old grease comes out of the back of the axle and fresh grease emerges. This system is awesome, if used right. Essentially, you are changing your grease several times a year. I put a bazillion miles on my previous E-Z Loader and am putting a bazillion more on my current one with zero rebuilds.
I've heard they don't make them anymore due to guys leaving grease everywhere, instead of catching it and disposing of it properly. If so, that's a real shame, because it was an excellent system.