So, according to mw.org, REL1_29 is due to become EOL this month. No specific date, or trigger, just June 2018. So we don't know if it's the start, the end, or when we released 1.31
As such, we should formalise a date to do this, send emails to wikitech-l, mediawiki-l and possibly mediawiki-announce for blanket coverage, and then make sure the mediawiki.org is updated as such.
Then we can start cleaning up CI jobs and other stuff we don't need to run anymore, and it also means I stop bothering Antoine and Zeljko with filing tasks like T197608: Selenium tests broken on REL1_29 :)
There is also the question whether we should (answer is probably) do a 1.29.3 release for maintenance reasons - https://github.com/wikimedia/mediawiki/compare/1.29.2...REL1_29 (37 commits), and possibly any pending security patches