I am about to start purging some old databases in our online system. I have databases dating back to 2006 in there and most of them are untouched trials. The purging will be done over a period of many months, starting with untouched databases from 2006.
What won't be touched is:
Databases that have an active paid subscription or
Databases that have an expired subscription less 12 months ago or
Databases where someone has logged into the admin panel since November 2020
So if you have an expired database that you want to keep around then be sure to log in to it.