From my perspective, I'm responsible for the internal management for PCO. I'm sure some of the issues you raised do exist right across the government. However, within PCO itself, I'm not aware of any particular issues around either the flow of individuals coming into or leaving the organization.
In certain divisions of the department, we do have a two-year window where analysts tend to come in from other departments, stay for a period of time, and move out. We don't consider that to be particularly problematic. In other areas of the department we have individuals who stay for long periods of time.