Really depends a lot on context. In my current role, we place a lot of emphasis on getting people through so it is quite rare I am still seeing someone after a year (though many return for boosters or another course later). Some exceptions obviously. DBT team keeps folks longer. Sleep team is usually < 8 sessions. From the get go, I encourage folks to talk to me about the process and be open about it.
In general, I will say that planning around the termination process was definitely something I found hugely overemphasized in graduate school and completely different from how it works elsewhere. Chances are, no conversation will happen and they will just ghost you one day. In hindsight, I think a lot of the grad school training was about managing the emotions of the trainees by fostering a sense of control than anything else. Your time for tracking them down will be limited. You may or may not even be doing your own scheduling. Many will be terminating for financial reasons. If someone's insurance drops, they are already hard up, and they need to pay $200 out of pocket to see you...are you really going to try and talk them into "just one more." I sure wouldn't.
