Here are the steps that the maintainer should take when an old Tor release series reaches End of Life. Note that they are only for entire series that have reached their planned EOL: they do not apply to security-related deprecations of individual versions.
A few months before End of Life: Write a deprecation announcement. Send the announcement out with every new release announcement.
A month before End of Life: Send the announcement to tor-announce, tor-talk, tor-relays, and the packagers.
Open tickets to remove the release from:
Close the milestone in Trac. To do this, go to Trac, log in, select "Admin" near the top of the screen, then select "Milestones" from the menu on the left. Click on the milestone for this version, and select the "Completed" checkbox. By convention, we select the date as the End of Life date.
Replace NNN-backport with NNN-unreached-backport in all open trac tickets.
If there are any remaining tickets in the milestone:
Mail the end of life announcement to tor-announce, the packagers list, and tor-relays. The current list of packagers is in ReleasingTor.md.
Ask at least two of weasel/arma/Sebastian to remove the old version number from their approved versions list.
Update the CoreTorReleases wiki page.