What one session does
It gives you information. Most people feel a change in range of motion the same day, and that tells us whether the problem is muscular and whether you tolerate the work.
What it does not do is hold. A muscle that has been clenching for years relearns its resting length over weeks, not in an afternoon.
The maths, published
Six to eight weekly sessions, then monthly to hold it. At the jaw price that is a real number and you should see it before you commit rather than after.
You get the series written down at the first visit with the dates worked backward from whatever you are aiming at. If the series stops, the tension returns. That is the honest version, and it is the same for everyone selling this work whether they say so or not.