I have some friends who take all essay-based a levels. They have said though sometimes it can be a struggle, as long as you stay on top of the work load you should be fine. As long as you generally enjoy essay-writing and don't mind writing for long periods, you'll manage. However they have said that if you aren't the biggest fan then maybe switch out one for another subject.
They have also said that some of the skills cross over with other essay writing subjects which may be useful!