its 6 where im living.
get some rest, then go through your notes 10 minutes before the first exam.
works for me.
my theory is on all nighters is your better off going to bed around midnight, then waking up again at 7am and do some more cramming, the good nights rest is pretty important as well.
never pulled an all nighter myself unless you call drinking 8 40's and not sleeping for 2 days an all nighter. haha.