That’s essentially what most people will do for their on-page search engine optimization and essentially this will work well. However as mentioned there are ways this could be better and in some cases this kind of search engine optimization can even backfire.
For instance, if you are using keyphrases too readily then this can backfire. For instance if you were to repeat ‘children’s toothbrushes’ ten times in three sentences then this would look like spamming to Google and like cheap tactics. At the same time the content would lose any value or interest. It would be too stilted for people to read and it would sound alien or strange.
Most people then would leave the site immediately then and not want to read it and that would then mean that your traffic was no longer good quality traffic and no longer likely to convert into purchases.
At the same time Google would of course not want to refer its users to these kinds of sites as that would not provide a good experience for them. Instead they would likely penalize your site which would result in its being moved down the page or even not appear at all. A bid to do ‘more’ search engine optimization then can result in the site actually failing as a result.
Meanwhile this kind of SEO on its own does not take into account the changes to the algorithm. Part of the problem with SEO is that no one knows Google’s algorithms and they are constantly changing meaning that you can’t perfectly tailor your site to have the absolute optimum number of keyphrases, and you can’t know precisely where to include them.
However we can make educated guesses and we can try to protect ourselves against future changes to the way that Google works and its algorithms work.