Ask HN: How early is too early to apply to a startup?

I'm currently a student in my last year at college, but I won't meet my graduation requirements until August after completing certain summer courses because of a voluntary leave of absence that I took last Fall. I'm hoping to find a job with a bay area startup company starting in September or October for after graduation. With the applications that I've sent so far, I can't help but worry that I'm applying too far in advance to small startup companies with unpredictable futures. So with that, I turn to you with the question, how far in advance should I be sending job applications to small startup companies? How early is too early?