Evergreen content decays because the SERP moves around it while the page stands still. Ranking is relative, not absolute, so a page does not need to get worse to fall. The results around it only need to get better or change shape, and observed behavior is that they usually do. “Evergreen” describes the topic’s durability, not the page’s grip on its position. A timeless subject still sits in a competitive, shifting marketplace of results.
The most common driver is fresher competition. Other sites publish newer pages on the same topic that are more complete, better structured, or simply more current, and as they earn signals they push past a page that has not been touched in two years. Intent drifts under the same query, too. The people searching a stable term may gradually want a different angle, a comparison, or a how-to where they once wanted a definition, and Google realigns the SERP to that new dominant intent, leaving an older page the wrong fit for a query it used to own.
Two more forces act on supposedly timeless pages. Facts go stale even on durable topics: figures, versions, named tools, recommended practices, and examples date quietly, and a page carrying outdated specifics loses trust signals and reader satisfaction even when the core idea holds. Google’s freshness weighting for a query can also rise, often after a news event or a wave of new coverage reframes the topic, so the algorithm starts favoring recency on a query that previously rewarded stable references.
The takeaway is that standing still is itself a slow decline. Treat your evergreen pages as living assets and refresh them on a schedule, updating facts and examples, sharpening the angle to the current intent, and adding the depth that newer competitors brought. You are not fixing a broken page, you are keeping pace with a SERP that keeps moving, which is the only way a timeless topic stays ranked over time.