Asset archival , Is there any OOTB feature which can be utilized to archive old assets?
As per my understanding from this based on some event or property or some other logic you wish to move this to some archived folder accessible to not all but few members or groups. Try using event listener and based on that you can do any operation. Review help link here https://helpx.adobe.com/experience-manager/using/events.html.
I did thought of Events, but not sure about its usability since there will be many many assets.
Any other approach you can think of?
You can even create cron job which runs say daily at 2:00 AM for example and that triggers move of assets based on say lastmodified date or any other property change. This would be heavy for first time but subsequent runs would be lighter.