Precisely why I absolutely try my best to avoid these overnight USA - HKG flights. Let's say CX 845 with block time of around 16 hours. Suppose you stay up for 3-4 hours by eating the whole meal slowly until 5am Eastern. That's still 5pm in HKG which is way too early even if you manage to sleep 10 hours straight. Having breakfast at 2/3am is really not my thing (and you can't avoid it especially in J when they turn all the lights on at 2:30am).

This is why I LOVE my home port 807 flight (similarly, CX 885, CX 879, CX 831, CX 825, CX 837, CX 841 maybe). Board and eat. Food coma or fall asleep whatever due to the constant motion, but you won't last long. Effectively an extended afternoon nap. Then when you wake up it's around late morning/early afternoon HKG time, you can 'enjoy' the flight for a long time if in J/F. Land in HKG in the evening and get tired when you reach hotel/home. A perfect reset. But then probably negates the need for a perfect sleep which is the forte of F...