i dont clean them unless they get dusty or something. cleaning out the insides makes it like new and static becomes a problem when switching powders. with use a powder measure develops a thin residue that makes it easier to empty and throw charges more consistantly.
i would clean the insides unless you REALLY need to.
"Gun control: The theory that a woman found dead in an alley, raped and strangled with her panty hose, is somehow morally superior to a woman explaining to police how her attacker got that fatal bullet wound." — L. Neil Smith