Back in the olden days (2015-ish?) KLM was having a really, really cheap business fare sale JFK-AMS; I snagged it with Delta miles (if I recall correctly) - and flew there and back in their 747 in the upper deck (just to take the flight; didn't have anything to do in AMS). It was really quite nice; it was the first and apparently last time I've taken the 744. I'm really glad I was able to do it.

Lol imagine sitting through 8 hours of agony for no reason. Do you actually enjoy flying? I'm sure I would find it agony even if I had the Emirates suite with the bedroom and shower (which is still more cramped than a 50 euro hotel room)

I would at least explore the city for a few days to have a break.

The only flying I enjoy is when I'm the one in the front left hand seat holding the yoke :)