Originally Posted by worldclubber

Talked to the purser on a recent flight and he said he always sets it to 20C (68F), which is the lowest the system allows him to do.

His theory about people complaining that it is too hot was that they eat a lot, drink (too) much wine and wear the wrong clothes. And he's probably at least partially right. I have now moved from wearing the long-sleeved PJs LX provides in F to just wearing the pants with a short-sleeved t-shirt, which helps. The duvet they provide in F is still too thick, but the one in J is much better in that sense. If you are prepared, you should be fine and do talk to the FAs when you are too hot, so that they can at least change the setting to 68.