If a leader’s direct reports are doing the same job, with the same responsibilities, two years from now, the leader has done a poor job. A leaders job is to grow their direct reports and prepare them for added responsibilities or to be moved on. Often leaders fail to groom their direct reports because they don't have a succession plan for the activities currently being performed.
What if a direct report suddenly leaves? What is the succession plan? It’s easy for leaders neglect the important, not urgent task of planning for a direct report’s succession. Part of each direct report's succession plan should be to have all key job functions documented. Leaders should make it the direct report's responsibility (maybe one of their quarterly goals) to create the documentation.
Knowing there is a plan should something happen to direct reports will allow leaders to further empower them to grow and succeed in their current role or a new one (and allow the leader to have a successful night’s sleep).