I did quit WOW by selling my account, but I am tempted to start again . Even if I am bored with it, the fun was in the beginning when neither I or anybody else knew nothing about the game, now I know everything, and there are things I would change
I think quiting because you have too much and become bored is the only real quiting from anything.
I think it applies even to drugs - but they kill you before you get bored