Yes, they give the content area the most weight in regard to individual page topical focus, however search engines do evaluate every word on a page, including content within the source view that visitors don't see. This is why having too much content in header, sidebar and footer areas, or too much code at the source view level causes topical confusion / topical dilution and is considered during the duplicate content evaluation process as well.
The best I can offer in regard to how often a phrase should appear on a page is "does this feel like I repeat this phrase too much?" If you've got the same phrase repeated fifteen times just in the content area, there should be a valid reason other than just SEO reasoning for that. And a LOT of text around those.

