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Yep. Spot on advice from John. I always like to keep in mind how your page content would sound if you read it out loud. If you're not sure, do exactly that, preferably to a friend and get them to tell you when it sounds like you're labouring the point. Always, ALWAYS make the user experience your primary focus. If you can clearly explain to the user what it is you're offering - without repeating yourself endlessly- then the search engines will be smart enough to pick this up. Now there's no harm in using your keyphrase (and synonyms) a couple of times throughout your content but only when it's needed for clarity. I understand how Yoast's SEO plugin can give you green light fever, but as is often the case, less is more.