One thing I don't get is how does one study when they have a double exam?
Depends on which two exams?
In most cases, you should try and aim to be ready for any exam about a week before (I know that this is sometimes unrealistic and definitely not something that I have stuck to, but either way it should be the aim hahaha). That way, even if you have two exams on one day, you should still be prepared
That doesn't sort out the issue of burning out/hand cramps after one exam going into another, but if you do practice papers under timed conditions, one after the other, you can probably train yourself to deal with it better.
So yeah, if that happens to you (I know it happens to me at one point, SOR1 and history extension
) maybe try and do a mock exam day, and do one after the other, giving yourself the same amount of break time in between, and see how you fair?
Hope this help!