I presume you would want to do this as keyword optimisation strategy. It is not good to over repeat words and expressions in an attempt to make good your chosen keywords. Google and other search engines may just devalue your hub for keyword stuffing.
One way to tell that your hub is suffering from keyword stuffing is the unnatural manner in which it reads or sounds. If your sentences and expressions do not flow naturally, you probably have over repeated some words, and which should be revised.
A better way to repeat keywords involves the use of synonyms. this too should be done wisely.