Was previously using "Schedule Filters" but this Add-on is super old and no longer supported on newest TB version. Hope for this add-on being upgraded is clearly hopeless.

Looking for an alternative or another approach to migrating/moving "old" mail between folders based on the message's age and it's assigned tags.

I managed to install Shedule (sic) Filters in TB 60, and it appears to work so far as being able to set the time, but I haven't fully tested it with an existing filter. Open Tools/Options/Advanced/General/Config. editor and double-click the preference extensions.strictCompatibility to false, OK to close Options. To install the add-on, drag the Download Now button onto Tools/Add-ons Extensions in TB.

https://support.mozilla.org/en-US/kb/installing-addon-thunderbird

Another approach is to create a filter as in the attached picture.

Thanks for the follow-up. I will try as you noted to install and test the Schedule Filter add-on. Regarding the attached filter suggestion. I have created similar filters and the filter side of things is good. The filter works as needed with manually run. The issue is getting the filters to run unattended/scheduled, so I don't have to remember to invoke them manually.

So far it appears that the Schedule Filter add-on runs correctly on TB 60.3.3. So aside from future risks of its obsolescence and exposure/care needed because the TB Strict.Compatibility protection has been switched off, I am proceeding forward with Schedule Filter installed.