Each monitored site has an audit_frequency: manual, daily, weekly, or monthly. The cron-nightly script picks up sites whose next_audit_at has passed and queues a fresh audit.
Defaults per tier:
- Free: monthly auto-audits.
- Solo: weekly.
- Pro: daily.
- Agency: daily.
You can re-audit any site on demand from /app/sites/{id} via the Audit now button. That doesn't reset the schedule - it just runs an extra audit and stores the result.