You should aim to revise for it just as hard as all your other AS levels because:
A) An AABb (for example) is more appealing than an AABd/c. Since your going to be up against other applicants (assuming you want to go to uni) with four AS levels and 3 A2 your AS could be be the difference between being rejected or accepted.
B) In the unlikely event that something goes wrong in one of your other subject and you are not allowed to carry it on to a2, maths will give you a good grade to fall back on.