Well, these are long flights. Our experience has been that the longer flights are equipped with bunk facilities, so any two pilots can be sleeping while the other two are flying the aircraft. These flights are, if anything, safer, because the pilots have sleep opportunities. They take advantage of them and they sleep more on these longer flights.
It may be that the longer flights are actually, from a sleep perspective, better than shorter flights, because one has more opportunity and one generally takes it.