What Actually Clears W3 Total Cache's Page Cache (It's More Than You Think)
A 30-day cache lifetime, and still the page cache kept shrinking overnight. Tracing every code path that purges W3 Total Cache turned up a purge policy that applies to far more than posts, a menu save that wipes the whole cache, and the reason priming right after purging does nothing. Then the purge log caught the real culprit: an SEO plugin wiping the entire cache every time someone opened wp-admin.