If we add a template on each page right now, the timer is reset until 2024.

So the idea would be to allow for a specific prefix to include a specific warning.

For example configuration could be:

$wgWarnNotRecentlyUpdatedDelay = 365 * 24 * 3_600; // One year

$wgWarnNotRecentlyUpdatedPages => {
    NS_MAIN => {
        "Operations grimoire/" => "MediaWiki:Old technical information",
    },
};

Documentation: https://www.mediawiki.org/wiki/Extension:WarnNotRecentlyUpdated (work in progress)