It's more than a good idea, it's *necessary*. (I'm a Joseph Campbell fanatic, so bear with me.) In order for the Hero to come into his full potential, the Mentor has to leave the stage. Take, for example: Obi-Wan Kenobi in the original Star Wars; Merlin in the Arthurian legend; Giles in Buffy the Vampire Slayer. The Hero's big finish has to be done alone and this means the Mentor either has to die or hie himself off somewhere a fecking long way away. I don't see Dumbledore walking out on this one, so...

*gets started on interview questions*