From both worlds
I am an instructor and a student. I have been teaching all the local guys to fly RC Helicopters. I have been flying those for 3 years and that's all I have ever flown.
On the other hand I have never flown planes and just got done building my Sig LT 40. I am remembering how exciting it can be to have that new toy sitting on the shelf. Now that I have the darn thing built I am waiting for my instructor to return. I have to wait 2 weeks before he can help me with the finishing touches.
The advantage I have is that I taught my instructor to fly Heli's now he is going to teach me planes.
I guess my point is it's a give and take thing. You have to give of yourself in order to recieve the help when you need it.
I feel your burn out frustration as I wasted an entire day waiting on a guy that never showed. Trust me I won't do that again. My suggestion is set rules for your students. If they don't follow the rules drop em to the next guy. Eventually they will get dropped or they will catch on.
Another suggestion is that your club makes a standard set of rules that ALL students MUST follow. This will protect all the instructors in the club and keep all the instructors a little more sain.