Are these exams in March or May/June?
If it's the latter, I think that's extremely extensive, but it would help a lot if you could keep it up. But don't overburden yourself with revision now, if they're not for quite a few more months. If they are in May/June, just be creating neater notes and reading through your classwork for a while, then when it hits March/April, revise more.
If they're in March, then I think it's still a little extensive considering you'd be spending a whole day each week revising, and also, Art will probably take up a lot of your time too. Again, if you think you can keep it up, go for it.
I think the methods you're going to use are good, but make sure you mix it up sometimes and maybe make flashcards or something to help you remember formulas. But past papers are definitely useful for those subjects.