I was on the 744 for little over 2 years only, but I once did a DXB-HKG-DXB and came damn close to running out of our contractual duty time limit for a 4-man crew (20 hours)...
One Captain and FO flew it for the first leg, while the other Captain and FO were snoozing in the bunk...and myself and the second Captain flew it from HKG to DXB.
The only reason we were able to make the return trip was that the ground handling in Hong Kong is top notch...and gave us a 90 minute turn with a full upload of cargo.
We blocked 16 hours and 9 minutes...and just under 20 hours of duty for the day.
They stopped scheduling that paring soon after that...
That said, long days at Atlas are very common, but that one was very unusual since we have lots of crews on layovers, reserve, etc in both DXB and HKG. We do work long duty periods, but only to the extent that a crew change may not be possible. For example, we could certainly do (and have done on limited occasions) DXB-FRA-DXB, but the company schedules a crew change in FRA and we might go to the hotel, or we will DH back to DXB on the same aircraft...and btw, snooze all the way to DXB in the bunk!!
Snoozing for $$$ is a great thing...or at least, it was on the 744. Not so much on the 767
