The browser warning appears even for a cert issued by a non public CA you have told your browser to trust, and most browsers already enforce a 398 day limit, so unless you have cooperative users, you’re already (effectively) capped at 1 year of validity.

Most browsers do this for certs with a lifetime longer than 398 days issued after 2020, which is one aspect of why so many websites use a 1 year validity period for their certs.

Which industry do you work in?

The secret is that rats are committed Luddites. They chew through wires, but maintain and restore the elegant mechanisms of times long past.

You may expect that a few rats couldn’t roll a 6 ton stone boulder back up a hill, but rats are also capable of growing to very different sizes depending on their environment.