Postulating is good, but only when the work is done. And the work is never done.
That means choosing when to brainstorm is key. Don't meet in chairs. Don't meet in the conference room. Don't meet near coffee. Don't meet with phones. All these contribute to long-winded, off-topic and distracted pontificating.
But, more importantly, choosing who to brainstorm makes the difference. Get the wrong people to the table and you're doing nothing more than day dreaming — or significantly disturbing the workflow.
And if the work is never done, don't poke the workflow just because someone with a long title needs something to do.