I've once had a whole sector of a fintech go down because one DevOps person ignored daily warning emails for three months that an API key was about to expire and needed reset.
And of course nobody remembered the setup, and logging was only accessible by the same person, so figuring out also took weeks.
I'm currently on the other side of this trying to convince management that the maintenance that should have been done 3 years ago needs to get done. They need "justification".