The trick is not just falling so hard for your story that you're willing to do the research - it's knowing when to quit researching and then having the discipline to write. (And revise, and rewrite, and revise, and rewrite...)
The History Girls' excellent blog asked Chevalier when was the right time to stop researching and her short answer was, "Never." The long answer was a bit more illuminating, particularly for fiction writers.
But what about copywriters? How much research is enough? Unfortunately, the answer is usually determined by deadlines and budgets - neither of which, in the commercial world, have much respect for the writing process.
Which means the writer must be a quick study, of both subject matter and of the personalities in play - who are you really writing for? The customers, about whom you have reams of data (of questionable significance) or the CEO, the sales manager, or the marketing director (who hired you)?
While it's a conundrum and not one a blog can answer, I'll go back to Chevalier's answer, because she's right: as a writer, you'll probably never do enough research. And I can safely say you'll never quiet all the critics - book reviewers, editors, clients or the CEO's sister, for that matter.
It's frustrating, but the tremendous reward in this messy ball of wax is that writers are truly always learning.
Tracy Chevalier's latest book is set in northern Ohio. She spoke at commencement to Oberlin's class of 2013 - 29 years after her own class graduated from the school - and she gave the grads a lot of advice. Five of her points were supposed to be all about writing - but they can be interpreted broadly. Most of the advice was good, for fiction writers, copywriters, and everyone. My favorite bit was this:
Go on, now. Stop researching - and see what you can do.