I'm doing 5 - Bio, Chem, PE, Maths and F Maths.
I didn't set out to do 5, as I was going to drop PE but got a very high AS mark so thought I might as well teach myself A2. Then school managed to timetable all 5 subjects so I've been to lessons for all. The plan was to drop PE or F Maths if it got too hard, but over half way through the year and its fine. And I do have a life aswell, I dont spend that much time working really - last term I was training 4 nights a week, playing in orchestra and a folk band and still managed ok. But PE is a complete doss and I quite often don't bother going to lessons cos I can teach myself in half the time.
So in my experience I don't think theres any issue with taking 4 A2s if you've done 5 for AS, and you're prepared to continue in the same way. Further Maths will do your uni applications more favours than ICT.
As for five, I think its more personal. Its a bit more dependant on the set-up, subjects, teachers, homework levels and how much time you're prepared to put in out of school.