The Louvre needs to be set up something more akin to Disneyland: maybe with a hotel on the premises and a week-long pass available. I think at the very least some kind of 1/3 price ticket should be available that lets you just see one section of the museum (like just the paintings, or just the Egyptian goods, or just the statues...) I think it was the first museum where I ever actually started to become frustrated at finding MORE COOL STUFF. The brain cannot take so much in one day. Hell, even my camera couldn't handle it -- it ran out of batteries taking snapshots of so many things!
Just be sure to mind the pickpockets (you will find signs all over the building about this. Paris is actually kind of a nasty place.)