I'm actually wondering the same thing although I'm on The Master Cleanse which is also a fast.
I did it nine weeks ago for some digestive promblems and other health problems I was having. I did it for 40 days! I didn't really plan on going that long. I just did it in 10 day increments and it was easy to do.
I would definately suggest changing over to the Master Cleanse. It will give you the energy you need to make it through exams. It takes a little more work then just water but it's well worth the effort! Also, your not introducing "food" to your stomach so the change over won't hurt. Try it, I know you'll like it.
I felt great while on it the first time(40 days).
I'm now wanting to go another 20 days but I have an event right in the middle that I would like to take a break for. I was thinking of doing 10 days then taking 2 days to ease off then eat a little on the third and then start it again for another 10 days.
Does anyone know if this will be bad for my metabolism or actually good?