deeper - 1:07 pm on Sep 30, 2013 (gmt 0)
Just checking the titles of ranking sites doesn't give me a reliable hint. How to know if the sites rank BECAUSE or THOUGH the double KW? There are so many ranking factors.
At the moment I prefer to use the KW a second time as variation, for example as adjective. I suppose this is safe and Google should recognize the "same" word. And it's nicer to read.
Google usually knows that a certain verb, adjective and noun belongs together? For example building, builder, to build, built.