I pack the bearings full each time I grease. We’re in mud water on and off the throttle. If the bearings are packed full no water gets in. Having said that a factory lubed sealed bearing only has grease to the top of the first ball. If bearings are over greased the balls inside may tend to heat and slide as opposed to rolling. This makes sense for example in a motor bearing that’s over greased running a steady rpm. Our machines are on and off the throttle, in water surrounded be aluminum that pulling the heat away. So for me pack them full keeps the contamination out.