Godfrey I would also draw an analogy to what DeWitt discusses (disapprovingly) here:
DeWitt talks several times about "faith in doctrine" as if he thinks Epicurus had gone too far in several cases. I think DeWitt is on the right course in observing that this kind of thing is exactly what Epicurus was doing, but DeWitt is wrong in his analysis of the result, because Epicurus' position is much stronger than DeWitt's assessment of it. I do think DeWitt's right in talking about it in terms of "faith," (confidence is probably a better word) but the "faith" issue is really more like: "I'm never going to know everything I'd like to know, so where do I place my confidence? Do I place it in Epicurean reasoning based on things I do observe, or do I allow any and all speculation, even that which has absolutely no evidence to support it?" Epicurus chose to place his "faith" about things that are unseen in reasoning based on things that are seen. To me that's a decision I can fully agree with.
Observing that pain is short if intense but manageable if long also seems like going too far when we think of how bad pain can be, but the best way to look at this seems to me to be that we NOT consider it "clinical medical advice," but as a philosophic statement that addresses the bigger philosophical issue, which is: While continuous pleasure is available to those who can figure the problem out, continuous pain can never hold us in its grip forever (we have death as an ultimate cure for that).
Seems to me Epicurus is frequently taking this kind of approach, he's using logical reasoning to explain the big picture to us as a way of organizing our lives, while also reminding us that there's no god or fate to magically solve all our problems, and that we have to work our way through them as best we can.
I might as well go ahead and observe that I see myself making this observation over and over in multiple discussions, probably not convincing many people, but becoming more confident of it myself:
In my view, Epicurus needs to be understood as first and foremost a philosopher attacking the big issues who wants to know the truth about them. Epicurus wants the truth more than he wants happiness, because he's convinced that happiness depends on having a logically consistent understanding of nature. That means Epicurus is committed to talking about everything in a rigorously logical way, and he embraces big-picture logical reasoning, so long as it is based on evidence. That's the starting point for understanding Epicurus, not seeing him as a modern psychologist who throws logic out the window in favor of looking haphazardly for whatever seems to work at the moment. A modern clinician is going to want to dissect "pleasure" into thousand different components, but for Epicurus the first step in making practical use of the issue is to observe the big picture and gain the confidence that comes from the highest level logical analysis, that comes from observing reality and then concluding that is is reasonable to classify all pleasures *as being by definition* the absence of pain.