Creating a strict timetable may build pressure for yourself (this is a positive/ negative depending on whether you like working under the pump). The idea of a flexible one is good for people who like to know exactly what they are doing at a certain time.
But this is highly up to the individual, if you are one who struggles for time or if you aren't used to routine, then you may find yourself staying up late and jeopardizing your health without a timetable.
I will probably set myself a strict bed time, and make sure i sleep at that time every night. I have 30mins for any catch up work from the day before before i begin the night's hw. And then generally, the night will be flexible, given that i never eat consistently at the same time.
I will do homework/study knowing that i sleep by __ time. Good sleep= More attentive next day, learn better, and grasp concepts better= feel better about study/homework.