Back in the bad old days when I did all my long-haul travel in Y (i.e. not so long ago!) I was convinced that I had spotted a pattern. Much more often than not, the cabin seemed to be absolutely freezing up to the point when the meal service was finished, then it mysteriously became decidedly warm.

Would it be far too cynical to suggest that some cabin crew may adjust the temp in such way as to make life as easy as possible, i.e. pax wide awake for the meal and fast asleep a.s.a.p. thereafter?