The important thing to remember is that different people are different. Cutting short my sleep at the right time works well for me based on crew rest considerations for the flight which can vary from three or four crewmember flights all night(plus more) to 2 crew flights all night.
I have only very occasion found myself sleepy at the more important times of flight.
Changing time zone 2-3 days before flight would frequently not work for me as I sometimes go from days to nights and back to days with 36 hours in between. However, If you are fortunate enough to have this time period, from a fatigue point of view, it can work quite well.