I've pulled all-nighters when I did the 48hr group builds and foud it was fun to do once a year. As a teen, I used to work all night, then still have energy to work or play during the day. Now I'm much older, I find that since I work 12 hours day, then come home, work out, do house chores, then maybe get a minute or two on the bench, by the time the clock strokes 10pm, I'm ready to count sheep. I need at least 6 hrs a sleep a day or I'm a vegetable and if I'm not alert, then I make stupid mistakes, get frustrated, and quite modeling, so I tend to build when I'm well rested.