I sometimes think of paragraphs as little mini essays or subarguments which make up your whole essay - so I always try to organize my paragraphs like a mini version of an essay: a topic sentence introduces the main point for the paragraph, then you explain it by providing evidence and supporting it with secondary sources and then you finish up by a mini conclusion that leads up to the next paragraph. With this being said, your paragraphs should be as long as you need to put your message across and express your opinion on that subargument (so somewhere between 5-10 sentences).
The 3 to 5 sentence “rule” is intended to be a foundation to build upon. In my opinion, a paragraph shouldn’t exceed 7 to 8 sentences; however, content rather than length should be more of a concern. As long as the content is present, in most cases, length is irrelevant.