I guess it depends on each individual. At this stage, a SGN and a BKK trip, both sign on in NRT around 5pm on day 1, arrive around 2 am Japan time (on day 2). Call time for return flight is around 5 (ish) am JST, with a landing in NRT around 3 or 4 pm on day 3.
Oh yes, there is a rule that one cannot drink alcohol 24 hours before sign on on a layover trip, so, if one feels the need to enjoy a refreshing, alcohol beverage, one has a 2 hour window after arrival in BKK or SGN.
This is on the 787, can't speak for the 767