Normally do not nap on cruise. Don't go to sleepuntil 1 or 2 am nightly. Also up between 6:30 and 7:00 most mornings. I love walking around a quiet ship with a cup of coffee while most everyone else is sleeping. I may close my eyes for 10 minutes or so after getting out of a hot tub, listening to the ship sounds.
I can sleep when I get home. For clarification, I am in my late 60's
At home, I do frequently enjoy a daily 20 minute cat nap.