You might notice that the timestamps on your Active Directory integrated zones don’t replicate around to all your DNS servers.
The reason for this is probably that scavenging is not enabled at the zone.
Active Directory will first replicate this information when scavenging is enabled, because the information is really not needed when scavenging is not active on the zone.
Remember is will take some time, the timestamp will be replicated next time the client update its registration.
You can find a very good article about DNS and scavenging here: