Same for me; I think the foundation/devops should subscribe to site24x7 (or similar) and get warning for expiring certificates – on all production endpoints; It happened 3 months ago;
@diegop wrote back in October, "In the short term, we have corrected the systems which deploy the ic0.app certificate, we are adding additional probes and monitoring to ensure quicker status updates and response and we will follow up with a post detailing how to access the Internet Computer without depending on the ic0.app certificate to eliminate a “single point of failure”.
Hopefully the processes will mature as this platform evolves.
Plan, do, check, act - I think the check part needs strengthening.