actually, you dont really have to do such extreme revision if u have revised well for your past year exams!
I mean, math is really just a practice and there is not much to study and the concepts and quite... simple.
English is another practice, even synthesis.
Mother tounge should be easy if u just remember the neccesary words which come back to you easily since u already learned them ( assuming your a hardworking student who prepared for all her exams with a kiasu parent) and just practice the papers and keep increasing your vocab.
science is quite easy, dont spend too much time on the concepts and focus on the keywords. Memorise them all and look at the question and try and see what concept the question is asking for and use the necessary keywords and synthesize them into a nice sentence.
The end! Not much to it but requires hard work, confidence and sheer determination.
Good luck for psle!