I would maintain that churches in my denomination don’t transition from one pastoral leader to another with consistent excellence and purpose.
The overwhelming majority of our congregations do not have the resources to support two men in a transition, so congregations endure a time without a minister/teaching elder/pastor, which is called a vacancy. Even in situations where a pastor retires a time without a pastor is the norm.
Twelve to eighteen months would be an average amount of time for the process of one pastor leaving and another being identified and installed.
Tradition also has it that a pastor is expected to have nothing to do with identifying and installing a successor.
At the Gospel Coalition website Collin Hansen writes about ‘Gospel Integrity And Pastoral Succession’.
The article deals with the situation of churches with well known preachers transitioning to their next season of pulpit ministry, and the circumstances of the churches described here are different to our own, but there are some general observations that would serve any local congregation as they continually plan for consistent leadership.
Jim Collins writes in Good to Great that an organization becomes a monument to the leader’s outsized ego when it falls apart in his absence. Mindful of this problem, [Dave] Harvey [author of the book Rescuing Ambition] sought to put subsequent generations’ interests ahead of his own by setting up the church for success after he stepped down to take a leadership role in the Sovereign Grace network. But this wasn’t simply a matter of organizational success. Indeed, Harvey contends that succession testifies to what a church believes about the gospel.