Just go through an amount which you feel happy with at the time. Somtimes I can only do 20 - 30. Sometimes I can do 100. Don't burn yourself out when tired!
What you have to remember with the question bank is that, whilst there are hundreds of Q's per subject, many are repeated, similar or require the same technique but with different numbers.
You will find that eventually the QB will hammer home the principles that the examiner is concentrating. Then, even if you do come across a Q you haven't seen before, you'll have a god idea what is going on.
I first got the QB and thought 'bo**ocks - do I have to memorise all this?!'.
1 month later, I never got below 90% on any test I did. And I work full time. It does work!!
Good luck.
Anyone else start their Mod 1 exams at LGW tomorrow?