Comments have been made here that the lube system design for the axles is probably more intended for boating use where the wheels and axles get dunked into the water. I agree with that idea FWIW. I'm thinking that no greasing, or under greasing, is preferable to over greasing. You really don't want to put enough grease in toput pressure the seals and cause them to fail prematurely. That would be worse than doing nothing. I have no data to reference and support that opinion.
Here is a thread which I found helpful.
Good luck. vic