I think there are basically two ways to use chess coaching, if that's what you're thinking about :
- You take one 'check-up' lesson 3-4 times a year, and use it to identify your main weaknesses and get some practical study&play advices. However, you need to provide your coach with some good material (ie. a bunch of annotated OTB tournament games) to take full benefits from it.
- You take regular lessons (2-4 times a month) to analyze your games in some detail, and work between the sessions.
Of course, the second format is more efficient, if only because regular coaching sessions where your games are examined motivate you to play better and train much more regularly (at least it works for me !). It also helps to correct mistakes quicker. But as it requires more dedication and money, many people are satisfied with the 'check-up'.
I think you can relate to this in your field.
What is the answer?
I have given private music lessons for many years, and the format has been 30 minute lessons, once a week.
Teaching someone new to chess, I guess it would make sense to use a similar format, since there are several basic things that need to be taught that could be spread out over several weeks, i.e., piece movement, captures, and checkmate.
What is the format for someone not new to the game? If that person's biggest weakness is tactics, for example, do you tell her to practice tactics puzzles, and have a follow-up lesson in three months, kind of like a doctor's visit?