As the FAQ How does intrasite replication work in Windows 2000? explains, intrasite replication for naming context data doesn’t occur until 5 minutes after a change. This delay lets all changes transmit at once. You can change this 5-minute delay.
You might notice the parameter Replicator notify pause between DSAs (secs). This parameter determines the number of seconds between notification of directory service agents (DSAs). This parameter prevents simultaneous replies by replication partners.