They don't suggest that at all! Can you not read? The key thing you've just conveniently left out is this: overtime is only effective over very short sprints

They don't suggest that at all! Can you not read? The key thing you've just conveniently left out is this: overtime is only effective over very short sprints Operative words. VERY. SHORT. And overtime, in the context of the article and all the supporting literature, is working more than 40 hours. Worst still, you or your employees then become stupid. Unimaginative. Burnt out. They make silly mistakes. Does that sound like a place that will foster innovation and greatness? Is that the kind of company you want to lead? Kid yourself all you want with your 40-60 'optimal'. But don't cite actual research that says quite the opposite of what you claim.