I would finish studying and then sleep up until your exam. That's probably not the most efficient or effective way of doing it, but I could definitely sleep easier knowing that I'm done my studying.
Note: This is what
I would do. I can't guarantee that you won't wake up feeling like [censored] and forget your hours of study.
On a side note, I think it would be cool to have been up for 48 straight hours. Never done that before.
It sounds fun, but trust me, it's not. After the first day you feel horribly tired (obviously.) Once you fight that off, you just sort of coast along, and it almost feels like you're in a dream.