There may be a few ill-advised individuals using these but most knowledgeable people don't. It is very easy to blow a seal and get grease on the brakes. These things were designed for boat trailers that are often submerged in water. Having a hub full of grease keeps the water out. Dexter employees even advises not to use them
I will second this. I think you are referring to EZ Lube axles and by only injecting more grease into the hub you cannot see or visually inspect the bearings, races or even the brakes that all should be checked periodically. Dexter makes the EZ Lube axles and specifies in their recommended maintenance schedule to take apart and inspect the bearings once a year. So what are you really gaining?
