You get an author's premium membership when the total of your stories size times score exceeds 5,000. (Lazeez expresses it differently.)
Well, My latest story, Purcell, was 760 K ad a current score of 7.13. That's the second story of mine to qualify all by itself.
I know that these aren't particularly long for SOL, but Purcell was posted over 9 weeks.