Could i restore a backup of Active Directory older than the tombstone lifetime setting ?

Changes to the tombstone lifetime attribute in Windows Server Service Pack1

The default tombstone lifetime value has sometimes proven to be too short. For example, pre-staged domain controllers are sometimes in transit to their final destination for longer than days. Administrators regularly do not bring offline domain controllers into operation or resolve replication failures for longer than the number of days that is specified by the default tombstone lifetime attribute. Windows Server Service Pack1 (SP1) increases the attribute value from to days in the following scenarios:

• You use Windows Server SP1 slipstreamed media to upgrade a Microsoft Windows NT4.0 domain to a Windows Server domain. When you perform the upgrade, you create a new forest.
• You promote a computer that is running Windows Server SP1 to a domain controller. When you promote the domain controller, you create a new forest.

The original release version of Windows Server SP1 does not modify the value of the tombstone lifetime attribute when the following conditions are true:

• You upgrade a Windows domain to a Windows Server domain by using Windows Server SP1 slipstreamed media.
• You install Windows Server SP1 on domain controllers that are running the original release version of Windows Server.

Increasing the tombstone lifetime attribute for a domain to days increases the following items:

• The useful life of backups that are used for data recovery scenarios.
• The useful life of system state backups that are used for promotions using the Install from Media feature.
• The time that domain controllers can be offline. (Computers that are built in a staging site and shipped to destination sites frequently approach tombstone lifetime expiration.)
• The time that a domain controller may be offline and still return to the domain successfully.
• The time that a domain controller may experience a replication failure and still return to the domain successfully.
• The number of days that the originating domain controller retains knowledge of deleted objects.