I've never opened a coaster brake and haven't owned one for some 60 years. I have no idea what the grease actually does on those hubs. But, something I have thought about a lot is - what if someone takes that hub and rides down ... (Day 2 of Cycle Oregon, 2016 for example.) Or the wheelchair hub I dreamed up 30 years ago that could be taken into wilderness a wheelchair could never get to before. That hub failing? Maybe someone notices the guy never returned, maybe not. Do I want that on my conscience?