>>7707662
Faster sketches at first help. Then longer ones are more helpful once you are starting to understand the concept you are learning. So more quick ones to start with, then increase the ratio of longer drawings as you get better. You can repeat this loop every drawing fundamental that you learn.
Let's say you have an hour to draw. If you did 5 quick ones in the first 30 minutes, you could spend the rest of the time on whichever sketch came out the best, or on a new drawing or two.