I think there are times we need to think about the impact others when it comes to jobs like teaching. I have been an adult student and as a Workplace Trainer and Assessor, I have trained apprentices and unskilled staff in a multitude of positions.
As a student I felt my concentration slipping a number of times in class because the subject was boring or the lecturer had a drone in their voice which would put you to sleep.
As a Trainer, and having some experience as an adult student, I would break up my lessons to avoid such problems. If I had a slide presentation which was lengthy, I would put in a totally different slide to break the monotony. I also had things like smarties and mints on the students tables to help keep their sugar levels up, thus keeping their concentration high.