William Zinsser, a noted writer on writing, said, as quoted in Jon Winokur’s Advice to Writers:
Short paragraphs put air around what you write and make it look inviting, whereas one long chunk of type can discourage the reader from even starting to read.
I’m a big fan of short paragraphs, as you know if you’ve read about the rule of 42-14-2 in “Does your article pass these writing tests?”
Breaking up long blocks of text is almost always a good idea. It’s especially important when you write something for people to read online. People’s attention spans are shorter online than when they are reading printed materials. Also, people who are reading online tend to be scanning for specific information. Shorter paragraphs make it easier for readers to find the information they seek.
When in doubt, break up your long paragraphs into shorter blocks.