I did 6 ASs-basically the ones that you're doing but with Music Tech instead of Economics (technically a 'soft' subject, but a lot of work). Although I had no free periods, and had to stay behind after school (M Tech being a twilight course at my school), I didn't find the workload unbearable. I'm awfully lazy and didn't do nearly as much work as I should/could have, but luckily enough I still did reasonably well (although probably not as well as I could have).
In terms of doing six A2s: I would advise not. The workload/difficulty increases massively, and even if you are comfortable doing the work in term time, I'm pretty sure most people would struggle with it during exam periods. Unless you're really really interested in every single one of the subjects, it's probably not worth the potential sacrificing of grades