It seems to me that there should be more passenger feedback to airlines about this. It's one of my pet hates!!
Many of the colleagues that I fly with seem to imagine that passengers like temps of approx 25c on long overnight flights. As some people have mentioned, some cabin crew complain of being cold at night and so some pilots will increase the temp to please them, even though there have been no complaints from pax.
. This is much too high for me, expecially with the people the front having duvets and the ones in back, blankets. There is no way I could sleep in that kind of temperature.
As a generalisation, it does seem that central european customers prefer higher temperatures to those of American / British ones. I personally select a cool temperature of approx 21/22c on night flights as, as mentioned previously, you can always wrap yourself in your blanket if you're cold, but if you're hot, you're stuffed.
With only 3 temp zones though, I do appreciate that it's impossible to please everyone. Cooler rather than warmer does however seem to be the concensus. Let's hope more crew get the message soon! And please... do mention to cabin crew if you're not comfortable.
SS