Answer:
My understanding is that a paragraph can be basically any length, and the only grammatical necessity for starting new paragraphs is a new speaker being quoted. Therefore, one could write an eight-sentence paragraph simply by starting a paragraph, writing eight sentences, and then inserting a paragraph break. In theory, the sentences would form some sort of cohesive whole. They should be related, at least, but you didn’t ask about how to write a good 8 sentence paragraph. You could even start throwing totally random sentences in there if you really wanted to. My hovercraft is full of eels. But if you want it to be engaging, vary your sentence length and structure.