There are a multitude of coaching models and processes. Each has value and benefits. What is essential is that the coach understands the client so that they flex to what works best for them individually.
Because the number one indicator of success for a coaching relationship is the rapport between the coach and the client, it is essential that the process creates the opportunity for the coach to get to know their client and for the client to realize they are heard and understood.
The average length of a coaching relationship is one year. Of course there are coaching relationships that are for just a few months and others that last years. Often there is a period of regular coaching followed by periodic coaching. Best practices means determining a minimum time commitment to the relationship and process and then continuing while there is benefit to the client.