How does auto-renewal work, will my cert ever expire again?

Let’s Encrypt certs last 90 days, so we automate renewal rather than relying on memory. We install certbot or acme.sh with a scheduled cron that checks daily and renews ~30 days before expiry, plus a reload hook that restarts the web server so the new cert goes live with zero downtime. Once it’s set up correctly, you should never see an “expired certificate” error again. We test the renewal with a dry-run before handing over.