I remember as a new first officer 30 years ago returning from a Greek island in the wee hours asking the Capt if I could have a 10 minute nap.
I was woken about 20 mins later by his snoring.
It wasn`t a problem in those days.
Later as Capt, I made sure we agreed who was to stay awake ( he/she would keep there r/t volume turned up) and set some sort of alarm as a back up.