I'm doing an all nighter at this very moment, I have a lab report to write, then a test to revise for, then I need to start packing up my room.
I would not recommend 'cramming'. If you are not careful you can be so concerned with learning those few last bits in 10 minutes that when you get into the exam, you can only think of them and nothing else. It is far better to plan your revision and stick to a timetable.
Hmm not all night, but from say 8:00 pm - 3:00 am.. its ok it works, but yea def. not before the day of the exam... its better when u have someone else workin with u, not studyin with u, i mean mah sis revises for her GCSE mocks and me mah maths mock together.. it worked out alrite!