Quoted from “New features in Lotus Domino 7.0 Beta 4” on developerWorks:
The administration process (also known as AdminP) no longer automatically reverts name changes. It now requires the administrator to either approve or reject the name change reversion. To provide uninterrupted access to a user’s databases while a name change is in progress, there is a period of time in which both the old and new names are allowed access to the systems and databases. By default, this period is 21 days, but you can set it to any whole day value from 14 to 60 when the rename is performed. At the end of this period, the old name will no longer be supported.
In some situations (for example, when the user is away for an extended period and cannot accept the name change), the old name must remain active and the new name abandoned. In such cases, the name change needs to be reverted to provide continued access for the user. In earlier releases, the reversion was performed automatically at expiration time. With the addition of the new approval process, the administrator can now approve or reject a name change reversion.