Component : SERVICE DESK MANAGER
Out of the box the archive and purge rules are only designed to purge specific items, it will not know of nor attempt to purge any custom related fields. In order to customize the rules you'd need to go into the site\cfg directory and add them to the file:
Note that customization to this file is not supported, and there is a possibility the file may be overwritten after performing a future upgrade of the application or applying a published fix. It is recommended to make a backup of this file prior to any customization, and also after completing the customization.