Final answer:
The question addresses the duration of an instructor's approval letter's validity and the process for renewal, which typically involves reapplication and a fee payment. The exact period of validity can vary but is often one year.
Step-by-step explanation:
The question pertains to the regulatory requirements for maintaining professional certification or approval for instructors by a governing board. Specifically, the question is asking for the duration of validity for a letter of approval issued by the board to an approved instructor. Once the instructor has been approved, the letter of approval is valid for a certain period.
Usually, the period of validity for such an approval letter would be determined by the specific regulations or rules of the board in question. In many cases, this is one year, but the exact duration can vary depending on the board's policies. After this period, instructors who wish to continue their teaching must reapply for approval, which typically requires submitting a new application along with a renewal fee.