My son graduated from ND in May. Applied and Computational Mathematics and Statistics major.
He could have arranged classes to be done after Fall Semester and given the number of AP classes ND accepted he might have been able to be done after three years.
That being said, he graduated at 21 (and still is 21). I was fine with him staying for his senior year - he loved dorm life, loved The Observer. It was by far the best of his four years at Notre Dame (well other than 4-8). I wasn't ready to throw him in to the real world at 20. It is different for each kid and I can easily see a world in which I would have pushed him to wrap up early.
That said, he's an only child, the college funds from myself and my ex were well positioned. He knows that grad school is on him - and he's hoping to sock away the cash from his job as he decides over the next few years what he wants to do.
None of his friends wrapped up early in way - though most of them were engineers,