I work in IT and if you need to call someone when they are off, that’s a huge embarrassment.
Nothing should fall apart because one person on the team isn’t there. Nothing should ever be so critical that their absence is life and death. Never should there be a problem where only one person has the answers.
If you have to call someone when they’re off then you didn’t manage your team and their work properly, and you fucked up, big.
Yep, and conversely someone is a “bus risk” if they are that single critical person.