The long sentences that sometime appear in the Apostle Paul's letters is one reason that I am led to believe that he intentionally employs rhetorical devices in his theopneustic missives. For instance, long "sentences" in Greek are called PERIODOI. Rhetoricians and orators use them liberally in Classical treatises. Aristotle also provides explicit details on PERIODOI in his famed work, _Rhetoric_.
Richard A. Lanham (_A Handlist of Rhetorical Terms_, pages 112-113) discusses Classical and Renaissance views on periodic sentences. He notes that there are two kinds of periodic sentences (per Quintilian), namely, structured and unstructured types. We usually find PERIODOI that are more loosely structured in dialogues and letters. This could well explain why Paul's epistles often contain protracted SENTENTIAE.
According to Aristotle, PERIODOI must contain whole thoughts and avoid being too short or too long. The usual parts of a PERIOD are called COLA. That is because the colon is the basic constituent of a PERIOD. Lanham has much to say about the PERIOD that is of interest. I particularly like Cicero's remark that a PERIOD must not be longer than "four iambic trimeters." I'm sure that you poetry buffs will immediately apprehend the gist of Tully's thought.
Finally, the reason for a PERIOD is to suspend syntax. In other words, a reader doesn't know the writer's complete thought until he/she arrives at the end of the PERIOD.