Because newsletter templates are available in all variety of lengths and sizes, there is really no limit to the content that you could potentially write. Keep in mind, however, that you should probably keep down your word count to a level that people are comfortable reading. While you may think everything that you are spouting off is fascinating, it's helpful to first sit down and make an outline of what you want your main message to be, or what the major news is that you are trying to share.
Anyone who has worked on making detailed sites knows of the trouble that it can be. Creating HTML and CSS pages that are seamless and work on all browsers with no glitches can be tough. Making sure that you have the right content and working with the right style templates is a huge advantage, but for those who want to step it up even one more notch working with a shortcut and aid like WordPress is a wise investment of time.