All night-before, with a bit of reading now and again in the upcoming weeks.
I still got 4A*s, 6A's and a B, which is good considering not only am I deaf, but I hardly revised one bit.
It depends on the person how much they should revise, but I'm confident if I revised more I could have done better. I couldn't be bothered though, I tend to do much better than anyone else in my school if any of us never revised.
Just a word of advice, if you ever miss something or didn't understand something in class, find out! Don't leave it last minute as I did. Also, I recommend you revise at least a few months beforehand, which is more than I ever did.