Replica Purger#Purger is an EDirectory Background Processes that is responsible for removing entries from the Change Cache once all servers have seen that object's changes.
The default is to run for 15 minutes followed by a 30 minute delay. In earlier versions of eDirectory prior to EDirectory 184.108.40.206 (20801.46) the Purger would wait on the skulker to complete. In sites that have continuous amounts of changes it could be hours before it fired.
EDirectory 220.127.116.11 (20801.46) and later the Purger runs alongside the skulker. Further, the delay setting is now configurable. This can be set lower so that the purger process runs more frequently and objects are removed from change cache more quickly once they are seen by all replica bearing servers. 10 minutes is the recommended minimum so that it does not run excessively.