The 80/20 of content refreshes
80% of your traffic comes from 20% of your pages. Those are the pages worth refreshing. Identify them in Search Console (top pages by clicks) and Analytics (top pages by conversions).
Quarterly: refresh stats, dates, screenshots, and any year references. Add new sections covering questions that have emerged in the SERP since last update.
Annually: deeper rewrite — re-evaluate the angle, add new case studies or examples, refresh the meta tags, update internal links to reflect current site architecture.
How to refresh without losing rankings
Keep the URL the same. Don't change the slug just to add a year. Updating dates and content under the same URL is fine and actively rewarded.
Don't gut sections that are currently winning featured snippets. Expand them, refine them, but preserve the answer structure that earned the snippet in the first place.
After publishing the refresh, request indexing in Search Console and check rankings 7–14 days later.