You can divide the intentions of Search Engine Optimisation into rough categories which are by no means clearly delineated.

• Pages that you need to be as highly optimised as possible, and which you are prepared to modify over time to meet the whims of Search Engines.
• Pages that bulk out the site, providing extra chances for a search to find a bite on your site. Since these pages should run into the hundreds and thousands it is unlikely that you can ever manage to keep all these pages totally Search Engine Optimised.
• Mid ranking pages, pages that are important enough for you to put real effort into optimising but which comprise too much effort to revisit as Search Engine requirements change over time.

The important thing to consider is how will people locate your pages?

One strand of logic says:

"I can write two pages of reasonably optimised content in the time it takes to write one page of highly optimised content. So I get two bites at the cherry for the price of one"

This arguments falls down badly if you end up with two pages that only show up in the third page of search results, when one well optimised page could have been in the top ten results!

However you can argue this the other way! In a highly competitive field, the one highly optimised page may never rank highly for your chosen keywords, the page may only be found by a slightly off beam search, and in this case you are much better off with more pages of content.

The other point about content, is that extreme SEO techniques are time consuming and transitory, whereas content accumilates. Each good page of content you add now will still be useful in a years times, or even 5 years time.