It's well worth reading Graduation, site closure, and a clearer outlook on the health of SE sites but if you haven't got time:
- When a site starts to consistently receive 10 questions/day, we’ll consider it for graduation.
- If a public beta site does not produce consistently helpful content, and lacks the caretakers needed for flags and spam to get handled and our Be Nice policy to be upheld, it will be closed.
Is your site in between these two categories? You don’t have anything to worry about. Regardless of how small the site might be, you have a home here in the SE network. Spoiler alert: As of this post, no site which is currently active is at risk of being shut down.
There are discussions there about what it means in practice for smaller sites like ourselves, and links in some of the answers to discussions about whether some limited customisation of beta site appearance might be possible, so if that matters to you, you might want to participate there.