Homework vs Revision?

Hi,
Was just wondering what most people thought about this. I'm in my AS- year so I feel like any advice would be useful for next year also.
Basically we get set regular amounts of homework in certain subjects. In French we get set around 2 hours a week, but some of it is just 'note the corrections' or 'read through model essays' - revision and independent study. The teachers have not really spoken about revision for our proper exams, other than a few saying we should be 'doing some'. If we have tests regularly and achieve our target grades in those and doing the homework, what type of revision do you guys reckon you should do? How much a week?
In R.S. we never get set any homework, and I never study any at home, and although it's an A-level subject, I feel confident with it and know if I revise a month before the exams I should be ok. But has anyone any advice on how much revision we should be doing at this stage?
At the start of term when everything was exaggerated, they said around 12 hours a week (on top of homework or including?), but if I feel ok with a subject and have made revision cards, is there any need for this level?

Thanks so much