i put a good 10+ hours a day. i feel like im screwin myself if i put less. but what i do is i spend all day on 2 chapters/main topics (ex: Electrochemistry and Optics) and each day is a different subject. for example, today is orgo, and ill be covering Alkene reactions and Carbonyl functional groups. but i spend the entire day focusing only on these two subjects, looking at both EK and TPR information. tomarrow is BIO and ill be doing evolution and genetics. day after that, physics, day after that gen chem, then i start again with orgo. burned out? HELLLL YESSSS. but i keep going. i do make sure i go out at least once a weak tho, and sometimes i do 5+ hours a day just to give myself a break.
edit: im taking my exam in july/august depending on how i do on practice exams at that point.