It had been variable all along.
In the beginning of class 11th(April to July), I was easily distracted. I couldn’t study for more than 20 minutes in a stretch. Effectively I would study for only 3–4 hours a day exclusive of coaching timings.
After July till February(when the 11th syllabus ended), I started gaining some pace because of recurring mock tests and the fast pacing syllabus in institutes. I wasn’t able to increase my study hours much though but I turned more sincere. I could pull off some 4–5 hours of study each day exclusive of coaching.
In February, I was mostly studying for NEET, but I wouldn’t deny my 10% attention was towards scoring good in 11th exams too. So I’d do lesser practice and would read more theory(covered 11th NCERTs).
In a month before 12th, I had practiced a lot, organic chemistry and physics specially. That months I would study only for 2–3 hours.
I was more consistent in class 12th. From April to December(syllabus of 12th got completed in December), I would study for close to 5 hours, sometimes the peak would go to 6–7 hours too.
December and January-First round of extensive revision.(More focus on physics and chemistry because JEE MAINS was in January) Less pressure of attending coaching lectures. I could easily study for 6 hours a day. I would score low in full syllabus mock tests which was a motivation to study. I then gave JEE MAINS January.
February(Second round). I had to prepare for boards. Read one hour English daily. I’d focus on theory more. So I took to the NCERTs. In this month I had completed whole 12th NCERT of physics and chemistry along with back questions of most chapters. I remember studying consistently for 6–7 hours a day.
March(post board exams) and April. More rounds of revision. I was in the beast mode in these last months. I could easily study for 10–12 hours a day. Sometimes even more. I knew it was now and never. Hence such a spurt in study hours.
I’d like to add that 2 years/1 year is a long time period. It’s near to impossible being so much consistent as to study following a strict timetable throughout.
I wouldn’t deny that there were days when I wouldn’t study at all, sometimes not picking up the books for 48–72 hours.
I wouldn’t deny that I had wasted a lot of weekends when I’d just sleep or study less for only a couple of hours. However most of the times I’d utilise weekends efficiently.
I wouldn’t deny that I had bunked quite a few lectures at coaching, thinking I would prepare some topics at home. Many times I wouldn’t, instead I would just waste my time distracted.
I wouldn’t deny that many times I wasn’t able to study all the three subjects on a single day. I would keep on solving physics and chemistry for days without touching biology. Ideally I could read only 2 subjects a day during general preparation and all 3 subjects a day during revision months.
I’ll reiterate like I do in every answer, hours doesn’t matter, it’s the topics completion, practice and revision is what matters at the end.