Buried somewhere in all those newsletters you get from various SEO firms, you will find, believe it or not, an admission by a prominent SEO opitmization "expert" that they had simply invented a supposed optimum size of 250 words for Web page text.
Different "experts" and SEO tools have often advocated various small page sizes. This seemed strange to me, because in comparisons, I found that the top pages usually contained thousands of words and the files were 60 KB or larger. Evidently, Web design firms invented this limit in order to be able to show clients that they were getting sites with many Web pages.
What is true of course, is that if you only have a limited amount of content, you may want to spread it over more pages to increase the page count of the site, which can help SEO up to a point. Likewise, it may be difficult, depending on your subject, to write in a natural way and still maintain optimal keyword density. However a really large and well written page can draw a hundred or a even a thousand times more visitors to your site than the average page, and it also presents opportunities for extensive embedded links to other pages in your site.
The page size optimum is one of many Search Engine Optimization (SEO) Superstitions I examine. The latest ones include:
Beware of contradictory and strange claims by SEO "experts" that don't make sense and contradict your own experience.