|Comedian Gabriel Iglesias|
Don't get me wrong, I LOVE brainstorming. Letting my imagination run wild with "what if" is a blast. You give me "nuclear physics" and I can get us to "were-chickens in outer-space." It's the best drinking game ever. Hell, I like so much, I'll do it sober with very little prompting.
However, when it comes to a story I'm actually going to write/am writing; that's me and my special weird having a grand old time before we expose it to anyone. Once we have, should my Dev Editor or CP make notes of "this is what I think you're trying to accomplish, this is how it reads, maybe try something like this," I'm all Gabrial Iglesias with the giggles, "Yassss, yasss!"
Every creative person has a different point in their process where brainstorming is most beneficial. There is no "right" answer just as there is no requirement that you take any of the suggestions hatched during a session. It's all about when and how you need your leeetle gray cells stimulated. (What? I know that's Poirot not Iglesias!)