I think it can be taken too far. One of my favorite series is by Michael Jecks, he was working up to a plot point involving the King of France getting married for the second (or third?) time.
But then he discovered the date he thought was wrong, and the marriage happened a couple months before. So he had to scrap that. But if he hadn't mentioned this in the foreward to the next book in the series, no one would have realized it.
He probably should have ignored history and kept to the original plan (it felt a bit jarring)