Recently on a flight I mentioned to a flight attended how rested they looked after 16 hours of flying.
I said it was warm at my seat and I could not get comfortable. What is your secret?
They said that they were very comfortable and are able to catch 4, 6 or even 8 hours of rest on a long haul flight like this. All of the crew are around for takeoff and landings however after dinner the one flight attendant that served dinner may disappear for a while.
On board there are special crew quarters and cabin areas just for staff. They are built below or above galleys and like at Disney World you never see the staff enter or leave.
Sleeping compartments are usually on the large planes like the Boeing 777 or 787 jets.