Create the expiration default within the system Options. Only new cards will have the expiration applied.
At the end of the day, when the store close is run, cards that have expired will be automatically be deactivated.
Create an system option to allow reactivation of expired cards. If reactivation is allowed then the expiration will be reset to a new term per the system settings.
Create a report of expired cards and have it print with the store close reports.
Product Support
Here is what I would like to see happen