You can only use a given coupon code once during the course of your membership.  i.e., You cannot use the same coupon code more than once.

From time-to-time we make coupon codes available to various organizations as a way to help their members.  You can only place one order with a coupon code during your membership.

We strongly recommend that new users with coupon codes wait until after they are certain they like our service to use the code.  Then they can use the code on one of our long-term, non-refundable subscriptions to get the maximum amount of savings from the coupon.