Final answer:
A bar to Reenlistment is reviewed periodically and can be evaluated at regular intervals or when there are significant changes in a service member's circumstances or behavior.
Step-by-step explanation:
The frequency at which a bar to Reenlistment is reviewed can vary based on the branch of the military and specific circumstances surrounding the bar. Generally, a bar is evaluated periodically to determine if the conditions that led to the imposition of the bar have changed sufficiently to warrant its removal. This review typically occurs at regular intervals throughout a service member's contract, and special reviews can be requested if there are significant changes in behavior or circumstances. It is not a static process and is subject to command discretion and the service member's performance and conduct.