Much like I think a DM should never have an intention on where the campaign is heading, and should instead simply present scenarios for the party to encounter, and let them deal with them however they choose... I do not plan where I want the character's personality to develop, only where he is right now. Seeing all the unexpected places that journey takes him is no small part of the fun of an RPG. Why in the world would you intentionally sabotage that by having plans for your character's personality development?