Lessons and training sessions vary in length as some lessons are only 2 minutes long, while others are 7 minutes long. There is also no cap on how many lessons you can watch in a row. Instead of thinking about lesson length, think about the time you want to set aside for each training session.
For example, if you want to practice for 45 minutes each training session, then you will have time for an exercise lesson, a warmup lesson, 1-2 lessons from your belt level, and a stretching lesson. If you have an hour and fifteen minutes to practice, then you should be able to fit in 2-3 more lessons from your belt level.