Content decay is the gradual loss of AI citations as a page gets older. Because live retrieval favors recently-published or recently-updated sources, a page that earned citations when fresh tends to be cited less over time. Often falling off noticeably after roughly three months (the "citation cliff").
This makes freshness a real ranking lever, not a vanity metric. Practitioner data has repeatedly found that AI citations skew heavily toward content updated in the last several months, and that a visible "last updated" date correlates with more citations.
The fix is a refresh cadence on your competitive pages, but the update has to be substantive (corrected facts, new data, added sections), not a bumped date with no real change. Definitional and evergreen content (like glossary terms) decays slowly and shouldn't be churned; reserve the effort for time-sensitive, competitive pages where staying current keeps you in the answer.