I've had some long procedures, my DS was 12ish hours (something broke with the lap equipment, and they spent a long time trying to get a piece of metal out of me). There is a direct correlation with how long I'm under, and how long it takes me to get my marbles back. I can say it was EASILY over a month of scrambled brains when under general for that many hours. Really not keen on that.
Because I don't like the long hangover from general, and also because I wanted multiple plastic procedures at the same time, and DO worry about the danger of it, I've also had several procedures under only sedation /twilight ( but actually asleep) and I prefer that.
Now, I'll tell you something about that too, since not all surgeons will do sedation / twilight, and not everyone wants that. I did wake up partially during two different procedures, and one time it was because they were closing me with metal staples on lbl and thigh lift and it hurt. It's just the vaguest memory, and I just said something to the effect of "wt%^&*f" and I heard him say "Deanne needs more...." and they gave more sleeping stuff. Barely a memory.
The other time I awoke during a breast reduction and was aware they were discussing golf and could feel generally what they were doing , but no pain. They didn't realize I was awake and listening till I commented on the course they were talking about. It was sort of interesting knowing what they were doing, but you may not like that. Again, neither of those times were what I'd consider upsetting, even though it sounds scary, and I still prefer twilight (but asleep) to general anesthesia, assuming it's not deep invasive surgery.