Long-lived stylesheets help repeat visits only when changed content receives a new address. Overwriting the same resource under a long cache lifetime can leave visitors with an outdated version.
Compare published asset addresses before and after a change. A content-versioned file might change like this:
/assets/shop.a1b2.css → /assets/shop.c3d4.css
A long cache lifetime with immutable can suit genuinely unchanging public resources. Do not apply that policy indiscriminately to HTML or personal responses.
Test an update as a returning visitor
Visit the page before a controlled test deployment, then revisit using the same browser context. Inspect both the HTML response and asset addresses. Testing only with an empty cache can miss update problems.
If HTML still references old files, inspect its cache policy and any CDN layers. Clearing one local browser cache does not resolve the delivery configuration.
Record the rollback path as well: earlier HTML needs its matching assets. Avoid immediately removing old files while pages referencing them may still be in circulation. Test a known subpage in addition to the homepage. Retain old asset versions while valid HTML responses may still reference them.