Ganondorf is basically immortal as long as he has the triforce of strength, IIRC. He could only be sealed, which only works for so long before he breaks out again. EDIT: oh wait, the master sword. Yeah that kills him, along with some other weapons i think.

But as to that king thing? I don't think he would stay king, if he kinda phased out into time and returned again. Or getsealed for a long time and return. You get my gist. ^^;