Break up your paragraphs to aid in the scannability of the page and to avoid walls of text. Readers scan for information and read on different devices with different screen sizes. Each paragraph should address a single idea in the fewest words and in the fewest sentences possible.
Don't make sentences longer in order to limit the number of sentences in a paragraph. Use shorter sentences and paragraphs.
A paragraph longer than 5 or 6 sentences is often an indication that the paragraph is trying to convey too much information. If so, break the paragraph into smaller paragraphs or remove some content. However, don't break paragraphs up if they contain a single idea. It's OK to have a paragraph with one sentence, and it can be OK if it's longer than 6 sentences as long as it's still about one idea.
Put critical information first
Similarly to putting the most important information first in a sentence, put the most important information first in a paragraph. Don't hide the key point of a paragraph at the end of the paragraph. Readers don't read every word.
Left-align text for readability. Don't center, full-justify, or right-align text.
Don't force line breaks (hard returns) within sentences and paragraphs. Line breaks might not work well in resized windows, across different devices, or with enlarged text.