I never add more than a few pumps. You don't need to press out "old" grease nor do you need to pump them until they bulge. IMO, it's a waste of $$$. Not much, I know, but there isn't any benefit to over greasing.
I grease my tractor trailer every oil change (10-15K miles) and my pickup every other. I have put over 250K miles on 2 different pickups and never had to change any joints. Granted, I didn't offroad very often. My old 85 Ranger used to get new joints frequently so it was never an issue. I beat the hell out of that truck!
There's more than one way to skin a hog...some just leave you with more meat.