I did something very similar to this leading up to trials and definitely advise against it. You will find that your study will become increasingly unproductive as the days go on, you'll loose a lot of sleep and become a general wreck by the time your exams begin (leading to poor performance within the exams themselves). Honestly, without the aid of study drugs (which i also highly advise against) I couldn't see any normal teenager keeping an eat, sleep, study routine for over a fortnight without crashing. As opposed to smashing out 10-12 consecutive hours of study, space your study out, take regular breaks and look after yourself. You will be surprised how much more productive and sustainable you are in the long run and will avoid risking your health in order to study.Weekends: ~ 10 + Hours
Weekdays: ~ >12 Hours
It goes without saying that 12-14 hour study days can have their benefits, but only when done in moderation. And believe me when i say this, you don't want to learn this the hard way.
So yeah, study smart and look after yourselves. GL for your trials.