After the first night, I had to rethink my initial plan to leave a yarn trail that I will later crochet into a blanket. The yarn trail would have impeded on the actual sleep training by being too much of a distraction. Also, after a strained wrist from winding yarn for only 4 trips worth, I realized the plan was not sustainable.
The length of my hallway is 30 ft, which means that each trip (walking to Mia's room and back to my studio) is 60 ft. 20 yards of yarn = 1 trip, meaning that the first night alone will have me using 1,320 yards of yarn. The new plan is to use this formula based on my tally marks.