Seem Google always check duplicate content of new site. I tried duplicate content onto another website, seems to be good at the fist or second week, after that the ranking is went down and down if still continue duplicate at the same way.
BTW, some site that contain duplicate content, mixed together with original content, still show high ranking and the rank increase when give it some back link(very few).
Google seem to get high rank for long term website and consider it more quality content(if not much duplicate). You will also get steady ranking and seem to be increased as far as you create unique content.