I recall the adage from a Woody Allen movie where he says "I have been working with my therapist for thirteen years and he thinks I am getting better."
I do not believe in this and want to see my clients move forward and get relief in a short period. Of course there are expectations when a client has a severe mental conditions like Schizophrenia or if the client fails to do the work.
My approach is to work with the client/clients to achieve movement. This should not have to take months and months.
Positive growth should be experienced within or at least begun within four to eight sessions.