OFAC Training Course Required Annually?

In general, BSA/AML requires training of all appropriate personnel, including the Board. You won't find anything that specifically states "annually." Rather, training should be ongoing. OFAC requirements are separate from BSA, but both are related. The FFIEC BSA/AML Exam Manual states:

While not required by specific regulation, but as a matter of sound banking practice and in order to mitigate the risk of noncompliance with OFAC requirements, banks should establish and maintain an effective, written OFAC compliance program that is commensurate with their OFAC risk profile (based on products, services, customers, and geographic locations). The program should identify higher-risk areas, provide for appropriate internal controls for screening and reporting, establish independent testing for compliance, designate a bank employee or employees as responsible for OFAC compliance, and create training programs for appropriate personnel in all relevant areas of the bank.

It also states:
The bank should provide adequate training for all appropriate employees on its OFAC compliance program, procedures and processes. The scope and frequency of the training should be consistent with the bank's OFAC risk profile and appropriate to employee responsibilities.