Future therapy or coaching appointments are set at the end of each session unless other arrangements are made. Scheduling of any future sessions is entirely up to the client and the client may stop making future appointments at any given time.
Therapists do not suggest or guarantee that a certain number of sessions will alleviate the presenting problem. Progress in therapy depends a great deal on the work the client is willing to do in-between sessions.
Written estimates are available, but many variables can change the number of sessions projected. Sometimes therapy can be like peeling an onion. You peel one layer back and another layer, or in this case problem area, may surface that wasn't originally acknowledged.