For long, the 'Gurus' claimed that long articles tend to bore the reader. Obviously, a reader who is not impressed with the first paragraph can quickly move away.
Panda or Penguin, the morale of the story is that every 'article' should be useful to the reader. The boneless Ezine articles, particularly those before Panda is a case in point. Pillar articles can hold the visitor on your website for several minutes. Aggregating all that is relevant to a particular topic and skillfully presenting it can be done only by experienced 'writers' wherever they are on this planet.