I remember our first cruise...it was on HAL. Don't ever underestimate older people.
There was this guy named Manny and his wife - both were in their mid-70's at the time - and I don't think they slept more than 4 hours a night. They would be at the karaoke, dancing up a storm in the disco, they'd be at the midnight buffet, and then I'd see them on deck at 7am the next morning. This was in 1992 so I wonder if Manny and his wife are still with us, but they lived it up in grand style on that cruise! I think it was their 50th cruise with HAL.