I think that would depend upon several things.
1. What type of class is he/she teaching.
2. Is the instructor the type to participate in the class for the duration for the duration of the class or does he/she put more emphasis on teaching.
3. Does he/she have a microphone?
Many years ago I was teaching about 20 classes a week. That was excessive for me.
When I teach now, I put more emphasis on cueing and less on actual movement.
Hope this is of help to you.