How to backup files older than X days shows some PowerShell scripts you could try to modify.
Backup files only if modification date > certain date in the past alternative is a changed files list.
You could test if robocopy can be persuaded to move old file trees somewhere for the backup.
<n> Specifies the minimum file age (exclude files newer than n days or date).
/move Moves files and directories, and deletes them from the source after they are copied.
rclone move might be able to do the same sort of thing.
–min-age Duration Only transfer files older than this in s or suffix ms|s|m|h|d|w|M|y (default off)
There might be other tools that can do this. I certainly don’t know all. You can also script your own.
I tried doing this manually in Explorer using age-based search, but the copy lost the tree structure.
Presumably you want the backup folder tree to look a lot like the original. If so, check tools for that.
You should be careful about retention to make sure Duplicati doesn’t delete an old backup version containing your only view of a given archived folder (a view after it’s deleted will no longer show it).
It’s also somewhat awkward to find out which backup is the only one that has a given archive in it.
all-versions can help, and you might use The FIND command too. The below provide some notes:
Add a global search for all versions of backup
Search across ALL Backups
If Duplicati were intended for archiving, it would have a different UI, but it’s a backup program that
does very well keeping multiple (similar) versions of files, allowing an easy restore of chosen time.
As a backup program, Duplicati also doesn’t hold the only copy of your filea, so problems aren’t as
much of a catastrophe. Duplicati is still in Beta, and (rather rarely) has problems getting files back.
So I think Duplicati is not a great fit for archiving then deleting, but if you insist, it can probably do it.