I've always used flexible schedules for our school time. When my oldest was in the early grades, one year I tried putting together a detailed schedule for her with specific times for each subject. We couldn't stick to the times, as anyone with several young children at home (especially with a baby) will understand, and my estimates for how long things would take were usually too high, but just plotting the work out like that gave us a sense of how much was realistic to expect in a day.
Since then, I've used other scheduling methods to help juggle the needs of multiple kids (I have four school-aged and one preschooler right now) as well as to train for independence. You can see more about how this has worked for us in these posts:
Sample Term Schedules
Organizing Our AO Year
Categorizing Our Schoolwork
Organizing Our Homeschool
This type of organization of our day really worked well for us, but for two of my four school-age kids it wasn't working as well as I hoped. One especially chafed under a system where he had certain work due by certain times, but disintegrated when given too much freedom. Another was struggling with the larger workload in the new school year and competing demands on her time. While my other two managed to find a balance, those two still hadn't, so a new plan was needed.
Rigid times don't work for us because our schedule for life has too much variability and with so many of us at home too many "crises" come up that derail a tight plan. However, I suspected that having times laid out might help these two kids the way they had helped my oldest, by showing what could reasonably expect to be completed by a certain point of the day and by clarifying the trade-offs involved in procrastinating. So I took the schedules I had already made (using the process laid out in the links). I decided on a reasonable start time for the child in question, then made a list of subjects assigned to times. For the younger child, each subject usually got about 15 minutes, but sometimes the slot was shorter and on occasion it was longer. For the older one, in high school, we used more longer time slots, with at least one being an hour.
These two students still have the same schedule we've always used, but where the others have an untimed daily/weekly checklist, these two have a timed daily checklist. That's more restrictive, but it makes them feel more free. The older one uses this as a guide to how much extra-curricular activity will fit into any given day. The younger one now sees clearly that certain work *has to* be done before snack time or lunch time or whatever. He sees that if he's even slightly diligent, all his work can be done in the morning. And he can look at the clock, compare that to his schedule, and see if he's behind or ahead for the day. I do hold him accountable to be caught up to his timetable before having snack, lunch, or free time--if he's ahead of the table, he can do what he wants to until the next timeslot, but he usually does several assignments in a row before taking a break.
From my point of view, this works exactly the same as the old way where certain categories of work had to be done by certain times. I don't go around with a clock or timer monitoring work. But the added structure of times has helped two of my students visualize this better, so it's been a useful tool.