Well, I guess it's going to vary for everyone. Depends a little on your priorities and how much time you can actually dedicate to art
What I am doing is finding as much time as possible lately and dedicating it to art study because I'm enjoying it a lot, heck I'm a hardcore gamer and am barely playing these days
I kind of arbitrarily set the time frame of 4 months per term (like semesters in a university) and during that time I watch the videos, take some notes in my sketchbook, and occasionally review them to make sure I learn the basic concepts for the long run. I try to practice every aspect in the term, not just do the assignment and consider that part done, rather I think you should at least get to a point where you are comfortable and satisfied with the work you can put out before moving on.
For term 1 that means in figure drawing, getting comfortable doing gestures, trying out different ways to do that by holding the stylus in different ways, changing the inclination of my tablet and getting used to doing gestures in different time frames, experimenting. Also implemented some traditional media so as not to become good in digital and not be able to draw with a pencil (I'd be kind of embarrassed IMO). Do a bunch of those cylinders and boxes of people, copy figures with proportions etc. I wouldn't move on if I didn't feel I am at least adequate at it. Same thing for the rest of the assignments and classes.
Apart from that, I would sometimes push myself beyond, trying to do constructions, trying to shade things, copying art with color but that's all stuff I'm doing because I feel it's fun and it costs nothing to experiment. Just have to do a balancing act. To improve I think you should definitely take it slow and focus on the simplest steps, not because they're easiest, but because they enable you to do more complex things later on. You need that foundation to be able to build upon
That said, it's easy to get lost in your own doodles as I soon found out, to get lost in experiments, and it's not a bad thing per se, just keep an eye on that and make sure you are actually also accomplishing the objectives of the current term
Wow that was long, sorry about that 
Good luck in the art school, and don't forget to have fun!
cheers
