You don't want to create long paragraphs. I break-up my paragraphs into short sentences...no more than 3-4 lines long. Some sentences are only 1-2 lines long. You want to have lots of white space and not a big block paragraph. Also, break-up your content with appropriate headings. Make sure that the font size is larger for your headings.

You want your posts to be long enough to get your point across, but not so long that you put your visitors to sleep. I think simplicity is a good rule of thumb. My posts and pages are usually 400 - 500 words in length. I don't know if the length of an article or post helps or hurts your rankings. Perhaps someone else knows better and will share this information. Hope this helps.