Critical thinking for me was a huge waste of time - I did it at AS for an hour and a half a week with a teacher who didn't really know what she was doing. All we learnt was that 'cranium' is a horrible game to play if you don't know certain songs and how to act them out (yet I managed to get an A???).
English literature A level, on the other hand, if you're serious about it requires a lot of time with reading and essays etc., but can be quite fun.
Speaking as one of the 2 people who did 5 A levels, 3 A levels is enough to get into med school, 4 if you like the subjects. so 5 subjects at AS, then dropping one to do 4 gives you enough time to do everything perfectly, with the insurance of an extra subject of you fail one (e.g. I did bio, chem, maths and physics - the bio and chem had to be As, and I had to get an A in maths or physics. English lit wasn't taken into account at all, nor the crit think AS, but as I said. lit is fun).