Unless you're using the ACME protocol with a certificate authority such as Let’s Encrypt, you're probably well aware of the annoyance of certificate rotation. Here at Datto, we use certificates in many places with a validity period of around a year, depending on the Certificate Authority. Last February, we noticed that several production hosts were providing expired certificates for one of our major Internet-facing domains - a mistake that many other companies suffer from, as well. This caused several problems, and it was decided that after the issues were addressed, we needed to take a very proactive stance in monitoring certificates for all of our TLS-enabled services. I will not dive into the details about why the certificates weren't properly rotated, but rather, what we're doing from now on so this sort of issue never occurs again.