This comes up occasionally, based mainly on David Eddings admonition to “Write a million words…then throw it all away…”. His quote is at the beginning of this article, and oft quoted elsewhere (like by Draft2Digital, the self publication site).
I’ve said it before and I’ll say it again–I don’t think there’s a magic number. With Against the Tide Imperial complete, I’m easily closing in one million published, someone actually is paying me for this, words and I still make face palming gaffes. Gaffes that make me want to just light it all on fire and never write again. Clearly there’s no magic number where the stupid switch gets a safety cover.
Yet, I can also tell you that I’ve improved as a writer. Remarkably. As in I see things I’ve written from high school and got ‘A’s on and wonder what the teacher was smoking. I’ve always dragged things out, dusted them off, and said, “That’s not bad at all…” with intent to maybe eventually publish it at some point. (This is the joy of indie–you can carry out a lot of “attrition warfare” at $.99/pop rather than have it sitting on your hard drive.)
Thus, if we’re being honest, I guess I’d say “Never throw a story away.” One, that’s like throwing away a piece of your soul. Second, just because they’re words 6,000-6,500 does not mean they lack worth someday. Finally, part of the growth process of a writer is getting external critique. If no one ever sees your work, how can they tell you what you do well?

Now if you’ll excuse me, I’m off to throw some more logs on the fire.