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If you mean - include *exactly* the same text all the way down the page...that might inhibit your ability to make sales, even if it does improve your rankings in Google.
What I do is, use the keywords where they make sense for the visitors to your site - you'll make more sales that way, have happier customers because it won't be confusing to them, and in return, they might recommend you to other people, link to your site, etc.
In short, optimize for the user experience & avoid "needless" repetition.