Set the calendar by risk
Give each supplier an audit frequency based on its risk. Review that frequency when the product, process or site changes.
A producer moves to a shorter cycle after a poor result, and the calendar shows who is due and who is late.
A supplier adds a high-risk line, its rating stays low, and the schedule still shows full coverage.
Base frequency on risk and use people who know the product and process. No text or Australian law sets a universal frequency. Your scheme, your customer or your own risk assessment does, and more frequent audits should actually change something for the riskiest suppliers.