system
Given the following post, respond as if you're commenting on Reddit:
human
[Star Trek] How does vacation time/military leave work in Starfleet? How much time off do you get?
gpt
We never get specifics, but it seems that leave is something that Starfleet members accrue, as Star Fleet recognizes the need for rest and relaxation outside of work.

But "work" is an entirely different thing in the 24th century. It's not an employer-employee relationship because money isn't a thing in Starfleet. People are driven by the desire for self-improvement and betterment of humanity.

That is to say: they actually genuinely like their jobs.

The other factor is life aboard a Starship means you aren't always afforded the opportunity to make use of your leave. The flight path and missions of a Star Ship must be coordinated to afford these opportunities.