Ahhh. What a room!
I've said this before somewhere here probably, but I'm reminded again by this photo: Modern monarchy is such a paradox: They are "heads of state" as it were, but with virtually no power. Then, there are the Queen Elizabeth II's and the Queen Margrethe's who seem to take a traditional attitude about it, wanting to reign for life, considering it a sober and important responsibility, ordained by God. They make the promise, and keep it.
However, modern life is such that people live for, practically, EVER! You have Prince Charles who might someday become king long after most modern monarchs have abdicated in favor of the younger generation. I find it a very strange situation, that one becomes king long into "old age".