Saban's ego also knows that there's not much left for him but to go down at Bama and the NFL part of his resume is less than stellar. He wants another shot at that.
Maybe, and at one time I thought he was egomaniacal enough to want the NC/Superbowl on his resumé. In listening to him especially over the past 5 years, I see him in a different light. He's more of a perfectionist/worry wart than an egomaniac IMHO.
I think, like Spurrier, he got a taste of the NFL and players that make so much that they are uncoachable and unbenchable, that he wants no more of it. Could be wrong, but I think Bama is his last stop.