I remind my team about their vacation and floater days on a quarterly basis and all them to be used. All I ask for is time for me to pivot as needed and if you have ongoing projects that you reschedule planned meetings, document as you go, and ensure access is available to the rest of the team if needed.
I've had employees in the past who I've sat down and directly asked them to take time off (paid) because they were burning out and would otherwise push through it. I've even reminded some of available leaves of absence for situations in their personal lives.
If the business can't continue without any one person, then the business isn't sustainable as-is and that's not fair to anyone. Hire more people if it's coverage or train your people if there's skill gaps. Documentation of systems and processes is also crucial.

A typo in software development or other shell based work could completely ass womp a system in ways that could lose a company lots of money.
Oopsies on prod systems, even with an outage window, can really fuck shit up. Seemingly small mistakes can quickly snowball into systemwide outages.