My T has said that some people have the sort of issues that can be mostly resolved in a short period of time, like a few months or less. While others have the sort of issues or conditions that might require therapy, maybe off and on, for a much longer term, possibly even lifelong. He seems to put me in the latter category, as I have pretty severe generalized anxiety disorder, recurrent major depression, and OCD. This was in response to my fear that he had all short-term clients, but he said it varies, how one has been with him 12 years (though not consistently). I was with ex-T for 6 years (probably should have switched sooner than I did) and current T just over a year, but twice a week (was weekly with ex-T, plus was seeing a marriage counselor for part of that time). I also take time to build up trust, and there can be the issue of dealing with things that come up in day-to-day life that can interfere with working on larger issues. So I figure it takes as long as it takes.
I don't know if I'm addicted--I probably was to ex-marriage counselor. I also have attachment issues, but they're something I need to work through.