Replace never lube bearing with traditional bearings

Harley is right, you would need to replace the entire axle assembly. I think the Nev-R-Lubes are the way to go unless you have an outrageously heavy trailer, wrong offset wheels, or the 42mm bearings. Mine are going on their tenth year but I haven't towed anywhere near 50k with them. I only average 2,200# per wheel on bearings rated for 8k axles. I carry a spare drum with bearing pressed in which I can change out roadside in less than a half hour with no chance of dirt contaminating the bearing. With the money saved from regular bearing maintenance over the years I could buy a 20 ton shop press from HF and all new bearings good for another 10 years. I do lift the tires at the beginning of the season and check for axial play and a free spin. No big deal as I am adjusting the brakes anyway.