- Create a query that queries for sustaining gift**.
- Use that query to build a group that rebuilds at least monthly.
- Create an Email Campaign that has nothing but that group as the audience.
- Create a self-copying*** monthly recurring message that sends to that group letting them know that their credit card has expired and offer them a link to update their credit card.
** If you do not have a Field Type of "Sustaining Gifts", call support.
***The Email Message must make a copy otherwise if the same constituent expires twice, s/he will not get the message as s/he has already received it.