I used to have assignments by block of time for homeschool lessons. Such as read history for one hour. I have changed that though, because procrastination or daydreaming can mean an hour long reading could stretch over three day's time.
I now give assignments by the page count or chapter or chapter section. Now it is up to my teens to start to learn time management. I make the lessons of reasonable length so they should be able to be done in the day before they go to afternoon sport team practice. Ideally they would do no lessons after practice, showering, and dinner. I say that because my sons are not in crunch time to cram in learning before a deadline at this time. That time may come but it is not this fall.
If my sons choose to dilly dally or daydream or they procrastinate or they choose to spent 50 minutes on the toilet reading iFunny on the iPhone instead of reading Biology on the can that is their choice. Then at night they can finish up their Bio. It's their choice. Read iFunny at night for fun or read it during the day while sneaking it in, but the schoolwork still has to get done. Period.
This leads me to a discussion of homeschoolers having "homework". I use the term homework to be assigned homework for any outside class including community college. The outside class's work does not take the place of everything else. My sons have to juggle their time to get it all done. For example for homework given on a Thursday that is due on Tuesday they don't get to goof around and have fun and ignore the homework until the day before then clear the slate of home-lessons to make way to shove in all the homework on Monday during the day (and then watch TV for fun at night).
I am more lenient than the teachers of the outside classes. I need to not be so lenient. I mean, I am not good about deadlines. My older son has stayed up late or almost all night to finish his Chem homework that was due at the co-op class in the morning, multiple times last year. However with the classes I oversee he would not do that. So I think I am going to have to have new rules such as "no going out for fun on weekends unless all the work that was supposed to be done on Friday is finished" or "if you do all your work you earn the right to go out on the weekend". The only problem is he does not always go out on the weekends, so, it's not a motivator or de-motivator.
Physical exercise is so important to one's health physically and mentally, and it is a way for my homeschooled sons to get socialization time with friends, so I do not want to have "stay home from practice" as a choice to do schoolwork that was un-done due to poor choices and bad time management skills.
One thing that is guaranteed with homeschooling is that it's a process that is always in flux.