Buenos Aires
I flew this trip several times last year and can assure anyone that it is very difficult to cope with the fatigue involved. Mention was made of the relief pilot, they (CO) also have a policy of giving the relief seat in First to a pax and then providing a center section three seater in coach as the relief.
There have been the occasional pilot who had to roust a pax from the seats when he got to the back for his rest or had to cope with lost pillows and blankets from to/top of climb.
Unfortunately, there are always pilots whom will kill for this kind of a trip. However, the truely safe way to handle the trip is to make it a 36 hour layover...........but that kills the productivity!
Two all nighters with a ten hour layover took me three days to recoup from!
Airmike767