I fly quite a bit across the atlantic with KLM (B777/A330). They generally have three F/D crew members: Captain, Senior F/O and F/O. A seat in Business Class is curtained off as an F/D rest area. At some point during the cruise the Captain will leave the Senior F/O in command whilst he takes a rest. At this point it is not unusual to see the Captain take a little stroll in the cabin and chat to the pax for a while before he goes to his rest area.