I'm doing it. It's tough when Drama has a deadline (public performance on 11th, then exam performance on 18th) and I have a commitment to the group so it takes priority. Teachers tend to be understanding. Apart from French teachers. Nope. French has gotta come first.
But other than that I really really love it. You'll suffer from a lack of a social life somewhat, but if you like being busy and you think you can cope, go ahead. If there is any kind of mentoring scheme at your place of study, I would recommend you sign up. My weekly meetings are life-savers.
Also all of mine are essay subjects - yes, including Drama and French. Lots of essays in both. It's not all bad. You likely won't get study periods with 5 - I have one a week which is spent on mentoring and EPQ meetings. It might suck initially ( I actually picked up an extra a few weeks in, so I really noticed the difference) but if you're going straight from secondary with no frees, to sixth form with no frees you won't notice that much. Either way, you'll get used to it. I'm keeping 4 on next year (hopefully) so having 5-6 hours free a week for extra study will seem like loads.
Good luck with GCSE's. I'm sure 5 will be just fine for you - but bear in mind, only do it with subjects you LOVE, or NEED for a uni course/job you will love.