Jerry's right. For 23 years I was throwing grease and changing bearings and seals every two years. Seemed like no matter what I did, I couldn't keep water out of the bearings. Got the Red Eye brand of bearing protectors at Northern Tool in 2004 and have not had any problems since. Red Eye has a indicator to tell you when you have put in the right amount of grease. As long as that indicator is showing, you know you have no leaks. I've never added grease since they were installed.