[syntheticnature]

If you let them quit instead, will you be able to find anyone(s) who will handle that work, and how fast will they get up to speed? And if the person's burnt out, is their schedule packed already to the point where things like "documentation" and "refactoring" are "nice to haves" instead of necessities?

[maratd]

This isn't black and white. The options aren't sabbatical or disaster.

Time off is not a solution. The problem will simply resurface when the person comes back.

The solution is to re-organize the work. Hire an additional person, if needed. Add work that the employee will enjoy and that will be relaxing. That's a solution.

If the company isn't interested in solutions, then the solution for the employee is still not a sabbatical. The solution is to quit and find a company that isn't so myopic.