What's your side projects success criteria for knowing it's time to leave your day job?

This is a bit of a personal question, everyone has different risk tolerances. Some of us have a mortgage and families to support with our full times, some of us are living nomadically without any dependents to worry about. Cover rent and you're good to go.

I'm just curious for those who are still working full time, what's your criteria for feeling confident that your side project has made it?

Are you saying X profit after Y months proves you should be good to go?

After making X in cash for Y runway?

Just curious.