How often is the design of the American flag reviewed for changes?

The design of the American flag is reviewed for changes "as needed," which reflects the understanding that alterations to such a significant national symbol occur only in response to specific circumstances, such as the addition of new states or significant events that may prompt a reevaluation. This approach ensures that changes are made thoughtfully and intentionally rather than on a predetermined schedule.

In contrast, reviewing the flag's design on an annual, five-year, or decade-by-decade basis would imply a regularity that does not align with how national symbols are treated and respected. The flag holds historical significance, and such decisions are made carefully to maintain its integrity and representation of the nation. Thus, the "as needed" approach is the most fitting answer for how often its design is assessed.