This article explains how long a budget membership lasts.
Each budget has an expiration date, which can be found in the budget card.
When a budget expires, a member can no longer enroll in courses. The members will continue to be a part of the courses they were enrolled in even after the budget has expired.
For more information or assistance, submit a support ticket to enterprise-support@edx.org, or reach out to your account manager (where applicable)