How long does it take to fix LCP on a WordPress site?

2 — 4 weeks for a real fix vs cache-only fixes.

The 4-day cache “fix”

Install WP Rocket, enable Cloudflare APO, claim victory. LCP improves by 30 — 50% but the underlying problems remain. The next plugin update or content change regresses it. This isn’t a fix.

The 2-week real fix

Plugin teardown (remove 5 — 12 plugins), inline above-the-fold CSS, defer the rest, async fonts, image pipeline rebuild (WebP/AVIF + responsive srcset), edge caching configured per page type. Result: sub-1 s LCP that holds through content updates.

The 4-week thorough fix

Above plus theme refactor to remove render-blocking JS, third-party tag audit (most marketing sites ship 8 — 14 unnecessary tags), and a Lighthouse CI guardrail so regressions get caught in the PR not in production.

The fix that holds

The fastest LCP I’ve shipped is 0.43 s on mobile p75 for a regulated-finance site. It took three weeks. It’s been holding for 18 months because the team kept the Lighthouse CI guardrail enforced.