What is the purpose of vocal exercises in general? What is the purpose of a specific exercise, given at a specific time? Why this particular one, right now?
If you are giving the same set of exercises for most lessons for all of your students, then it would seem you are not answering these questions. No singer needs the same thing in the same manner forever, although as my colleague Justin Petersen just posted today, there are foundational exercises that can go on forever, allowing for improvement of form and general fitness in the key areas of singing technique.
I think it is important to ask the second and third questions every time you do an exercise with a student. Knowing what an exercise might do for most people is helpful, and then there will be the times an exercise doesn’t work and you need to take a turn. You may have to create an exercise on the spot. Practicing creating exercises that are like other exercises in intent is a great exercise for the teacher!
But whether you create things extemporaneously or not, knowing which exercise from your teaching library to select for the singer is very important for problem-solving and progress. Each singer is a little different from the next, and each singer is a little different from their own self from the past. A teacher’s constant listening and analysis in the moment is crucial to serving singers at high levels.
It can be scary at first, but there are times when you must abandon a normal lesson and do very different things for a week or a month or a year, in order to address a specific problem.