Calls to action=raw seems to return dual (different, 31/30 day) max-age headers on 5.2.1 servers pretty consistently:
X-Powered-By: PHP/5.2.1 -- Cache-Control: public, s-maxage=300, max-age=2678400, max-age=2592000
X-Powered-By: PHP/5.2.5 -- Cache-Control: public, s-maxage=300, max-age=2678400
Categorizing as a Wikimedia bug, because it is probably domas's fault!
<brion> note it on bz or sth make sure it's not lost, will poke it later :D