From my personal anecdotal experience, I've found it worse when travelling east around the globe. I also tend to stay awake most if not all of the flight, so sleeping time doesn't tend to matter as the flights from London to NZ are minimum 28 hours. Shorter flights you can arrange around daylight hours to reduce this, but otherwise, there must be better strategies to help out with.
So I was fine despite nearly 48 hours of non-sleep from Mongolia to London, up the next 3 days at 8am to do stuff. However, the SECOND week has been awful, sleepless nights and erratic sleepiness. Any theories?
UPDATE: Flying to NZ from Canada tomorrow with a stopover in LAX, so should have some good jetlag. More theories welcomed.
Again, I was fine for the flight. Tired, and I did sleep in the next day but only to 9pm. Second week was not bad at all. It may have helped that for the LAX to AKL leg I was given an exit row seat. And I did find myself struggling to stay awake in my few hours of stopover time in AKL, and slept on my 1 hour flight to CHC.