USPS requires every boxholder to have unexpired identification on file with their Form 1583. PostalPoint tracks the expiration dates of both IDs on the form, including the address ID.
Run the Expiring IDs on 1583 report from System Menu → Reports to see which boxholders' IDs have expired or are about to. Ask those customers to bring in a current ID at their next visit. For a driver's license, scan the barcode to update their record instantly.
Running the report monthly, and mentioning it when a customer renews, keeps you from finding out during a USPS audit.