My T considers long term therapy to be therapy that lasts longer than 3 years.

In some types of therapy, such as IPT, it is decided at the beginning how many sessions you will have, usually 12-16, and at the beginning of each session, the T reminds you how many you have left. The T uses different interventions in the beginning, middle, and end. You always know where you are. Do you wish for this much certainty, SoupDragon? I can see that it could provide an anchor of sorts and not lead clients to get that "lost at sea" feeling.

I have been going to therapy for 4 years, and I think I will know when I am done when I no longer have anything to work on. So far we haven't run out of things, and new things keep coming up to deal with. I like that we no longer seem to be working on "old material" and are up to date, so we can just work on current stuff. That feels great! So one question to gauge where you are in therapy might be, are you still working on material from the past? Of course, in some therapies, they don't even work on stuff from the past...

Another way to tell where you are in therapy would be to ask your T. Your T has seen so many clients and might have a good idea, or might put his idea together with your thoughts to come to an answer. Or the two of you could explore your feeling that therapy is "mysterious, full of hidden agendas, dark alleys and brick walls." Could be a fruitful discussion! FWIW, I have felt that at times I did not understand what was happening in therapy, but I never felt there were hidden agendas, dark alleys, brick walls... I did have walls and alleys, but they were in my mind, rather than part of the therapy process. Therapy has helped me navigate them, uncover them, etc.