Let me start by saying that hypnosis is not a miracle cure, even though it sometimes seems to be. There are cases where the client is cured of alcoholism, drug addiction, or something similar in one session, but that’s not the norm. Therefore, you shouldn’t be disappointed if your habit isn’t completely gone after one hypnotherapy session.
The motivation to quit an addiction could be a significant part of success. Some people use hypnosis as a last resort, but they want to leave the habit so severely that they try anything. Such people are very motivated to quit the addiction, which makes the hypnotist’s job somewhat easier. These could be the cases where hypnosis can help in just one session. Others consult a hypnotist because they feel obligated to do so by a family member or friends. Such people aren’t that motivated to quit and are harder to work with.
This shouldn’t be seen as a dichotomy of whether your addiction can be cured in one or more sessions. The complexity of the addiction and the substance of addiction also has something to say. You can ask the hypnotist how many treatments he will estimate that you need, but it will be a total guess since your case cannot be calculated based on others; every client is unique.