Well, i completed my igces last yr and i was just as confused as you guys. i later realized that there were days where i spent 9 hours studying and still found a 30 min session more productive. although that might not help, its just what i found. i tried to create timetables but those didnt work out for me cuz i just didnt feel like doing a certain subject at a certain time. so instead i made a checklist of things i needed to do by the end of the week. I made this a full fledged thing around a couple months or so before my mock exams, which were about 4 months before the actual exams.
before my mocks, i really wanted to test myself to see how much i already know, so i went right into past papers, flipping through textbooks only if i was completely stumped and had trouble understanding the mark scheme too. before my gces, i did ONLY past papers cuz at that point i did know everything and i literally studied from the mark schemes because wording and key points are important. found out that i wasnt the only one, my teachers suggested taht a couple weeks later too. during the days of the exams, i only studied from condensed notes like: z notes. carrying my heavy textbooks around proved to be useless for last minute revision because after following the above mentioned i only needed to refresh my memory.
Good Luck Guys! Hope this helped!