Originally Posted by Sheldon Brown
There is never any reason to remove a freehub body from its hub shell unless you are going to replace the body...for overhauls, the body should stay on the hub shell, makes it much easier to work with.
I don't agree. All of the Shimano hubs I've worked on (105, Sora, Ultegra and Dura Ace) have freehub bodies with a rubber seal ring set in the rear face. Removing the freehub body lets me removing this seal so I can drip light lube (Tri-Flow or similar) directly into the bearings. This is much more thorough than trying to get lube to penetrate through the tiny gap in the outside face of the body. I do this during my annual overhaul and the freehubs seem to last forever and are very quiet.