I'm in year 13 now and currently wish to study history at university, what I found is that if you do genuinely have a flair and like the subject, no essay or work will be too tedious or not worth doing. The jump for me was miniature, I think this is purely down to my commitment to the subject, the new work didn't affect me in the slightest becuase I wanted to do it and I wanted to learn and become better at the subject. However a lot of other students who picked history because they sort of just didn't mind it, or thought it'd be a nice a level to have really struggled at times as they didn't want to work hard or commit themselves. The point I'm getting at is that if you love the subject, the extra work won't really be a problem, you may actually enjoy the new bredth and detail but of course if you don't enjoy the subject then, well, good luck!
Hope this helps! X