As someone who took 11 GCSEs last year I guess my best advice is: "PACE YOURSELF!" If you overrevise you can get stressed and burn out. I personally revised a little bit over half term for my mocks and after that, during Easter holidays, I worked every single day for about 4 hours a day. This allows you to still enjoy your holiday during the main part of the day and to do sufficient revision. I think it's too early to be revising now, however it's good to be compiling notes and looking over difficult stuff now. They key is past papers this term.if your school aren't already doing so, get some past papers done. We did about 20 for each science and maths and it's helps immensely. Good luck!