My instructor would fall asleep after 10 minutes of watching me do figure 8s in the sky. Now that I'm an instructor, I have inherited his trait. To remedy this problem, I use my own trainer. I'm amazed how much more alert I am when its my 2 bits kicking around the sky. Like Jim pointed out. I'm a firm beliver in lesson and flight plans. Give the student some homework and let them know what they will be doing the next flight and for how long. An instuctor can show a lot in 1/2 hour such as stall recovery, spins, how to maintain wings level and altitude. Very important skills for a new person to aquire. My tank only lasts 15 minutes and every flight has me trading off with the student every couple of minutes. Me showing the technique and then handing off to the student and talking them through it.

Where I see "dangerous Tendencies" appearing is when the student gets enough lessons to barely control the plane, then starts practicing aerobatic manouvers and moves into a 33% aerobatic plane. Kinda why I see a pilots who can spin, snap, and hover to their hearts content, but cannot takeoff, maintain and hold a pattern, and do touch and go's worth a penny.