§1. Superiors are to be constituted for a certain and appropriate period of time according to the nature and need of the institute, unless the constitutions determine otherwise for the supreme moderator and for superiors of an autonomous house.
§2. Proper law is to provide suitable norms so that superiors, constituted for a definite time, do not remain too long in offices of governance without interruption.
§3. Nevertheless, they can be removed from office during their function or be transferred to another for reasons established in proper law.
Source: Code of Canon Law (Vatican.va)