[forinti]

Just this week I had an issue with a Letsencrypt cert that wasn't updated.

All of my users had visited the site and the certificate was the same. Browsers should give a less dramatic response if they have already seen the certificate and it simply expired. It's completely different from visiting a new site whose certificate the browser has never seen.

[lazyweb]

On the other hand, especially when offering an online service, cert monitoring and/or robust automation are essential. Blaming browser behaviour is missing the point in my opinion.