Some decide to do it every other day over 4 sessions.
Some choose one two hour intensive session. They go through all the various scenarios of situations in which they smoke with their hypnotist and discuss alternatives. They're taught they have another choice and can easily function without them. Then during the actual hypnosis session they lose the urge. They have the will power to quit on the spot. They are in control. They are masters of their destiny. And they're taught self hypnosis.
The client is the judge of what's right for them.