Replications and other sling jobs are processed slower in AEM6.2 versus other AEM versions.
To validate if you are experiencing this issue in your AEM environment, then check the following:
In thread dumps you might see threads like the one below:
It is a known product issue.
A. If you do not use Adobe Target with AEM
...then you can safely disable Delete Adobe Target Activity Listener by doing the following:
Go to http://aem-host:port/crx/explorer/index.jsp and log in as admin.
It may take a long time to delete and tax the system greatly. To avoid an outage, you may want to browse to subfolders and break up the deletion up into smaller steps.
Right click a sub-node of com.adobe.integrations.target.deleteauthoractivity and select Delete Recursively.
Uncheck the Preliminary Scan box.
It may take a very long time to delete and tax the system greatly. Break up the deletion into lower subfolders if required.
After all deletions in the unassigned folder are done then repeat the same deletion under the cancelled folder /var/eventing/jobs/cancelled/com.adobe.integrations.target.deleteauthoractivity.
Deleting thousands of nodes can greatly tax the resources of an AEM environment. Due to this, you should wait for a time when few users are using AEM before performing the steps above.