If you think you could cope with the workload and that it wouldn't have a negative impact on your other grades, then go for it.
Education and Careers are about competing. You need to try to be the best. You need to try and get the most qualifications. You need to try and stand out above the rest. Give yourself every opportunity you can to get onto the course and university you want to. There's thousands of other applicants behind you, that extra AS grade might give you the slight advantage over them.
Take five, see how you cope for the first few weeks and if it's that much of a struggle, you can always drop it! But if you can cope, I'd say keep doing all of them.