5 AS is OK. I didn't have any frees at school with 5 subjects. Tbh, I didn't actually think it was a lot of work, the real jump seemed to come from AS to A2 now. It actually seemed like less, because there were less subjects. I took Maths, bio, chem, English lit and physics.
From what I've seen, Geo seems to be very essay based which might add to the workload. If you're comfortable with the workload now, you should feel the same about AS. Does Critical thinking have a lot of homework?