The Fine Line Between First Assistant and Assistant

It is such a fine line like that moment is really tricky and I've worked with and am friendly with quite a few other artists on their own and have recently left assisting but they've worked with some of the top top tier talent. Some people are happy with that and some people will assist forever and maybe grow into like a studio manager position or their producer or their agent. But then at some point you do need to draw the line because you're giving away your service he's diminishing the whole industry if you're continuing to do something for free how do we justify our time?