The EZ-lube system is really just for refreshing the hub with some new stuff. A feel good check you have some decent stuff in the hub.
Do not believe anyone who says the EZ-lube system blows seals. That is absolutely false, unless the seal is indeed bad. Only a bad seal will allow grease to pass!
But do remove and manually repack the bearings by pulling the hubs every 12k miles as directed, do not rely on the EZ-lube system.
Ironically, if you do manually repack the bearings every 12k miles or less, you really have no need to use the EZ-lube system.