I would leave it alone, and only lube when you have it apart when changing the
sprocket. The only bearing failures I ever see are from foriegn matter winding in there
and boogering up things. If you are not accustomed to removing a clutch, then your
bearing greasing thing could be troublesome, when there is nothing really to worry about. Some guys here are kind of anal, so you should ignore them.
Just kidding girls, I just like saying {typing} the word anal.