About 36 hours, give or take a few. Although that was an entirely voluntary all-nighter that I pulled a few weeks ago just to see if I could, I've inadvertently pulled several more by mistake mainly thanks to being side-tracked on the internet then thinking 'lecture at 9am, is it worth getting only three or four hours of sleep?' considering that it takes me at least an hour to go to sleep anyway often. I'm trying now to get my sleeping patterns back in order though, since I've been getting up at 5pm on some weekends and missing half my tasks for the day (which means I stay up late to do things like coursework and housework, then end up going to sleep really late again, and perpetuating the vicious cycle...).