I am a rubbish sleeper on planes. Doesn’t matter if I’m in economy or up front, I just never properly sleep.
I fly transatlantic a few times a year, usually for about a week. I usually have a day between landing and going back to work.
I prefer to upgrade the outbound day flight because I am awake/eyes are open so I’m more aware of being cramped in economy. I enjoy the food more then.
DP prefers to upgrade return overnight, which is usually about 1.5 times the outbound upgrade. I don’t see the point because I’m half dozing and the flight on the way home can be just 7 hours. On the way out it’s easily 9 hours.