[yebyen]

You don't want an alert to check the cert is still valid, that's how you get outages. It's an alert to check cert has at least 2 weeks or more life left in it! (So it either fires ideally before you leave for that long vacation, or so that you can still take care of it when you get back.)

[agjmills]

But also check it’s still valid, because revocations

[GauntletWizard]

This is all built in very nicely to https://github.com/prometheus/blackbox_exporter - Though they could use a blazing red link to an example rules file.