I agree with you I think Don, and I do see a distinction between long-term and longest time.
I also think that there is a possibility that this phrasing may be another targeted argument against Plato, and you'll recall that DeWitt discusses this as a point of contention, that Plato had argued that another reason that pleasure could not constitute the goal is that it is not always present (not continuous being the implication):
This first is from page 66
So while I agree with you again that there's a logical distinction between long-term vs longest, and duration of pleasure is certainly a legitimate consideration, I think this one may be parallel in nature to "absence of pain" - it may need to be "compartmentalized" as a logical rejoinder to an anti-Pleasure argument from Plato and the usual suspects, and as a result handled carefully outside that context, so as not to overstretch its application.
I am glad you posted that because otherwise I would not have gone back and looked up these sections in DeWitt, which I remembered only vaguely.
I think I am only now after 10+ years realizing the significance of some of these sections from DeWitt, and after our discussions here and in the Lucretius podcast. I read the words here, and I thought I understood them the first time, but it's really beginning to sink in to me how DeWitt is pointing out that Epicurus was both the ultimate pragmatist, and disdainful of dialectical logic, but also at the same time he responded directly to Plato in logical terms, playing Plato's own game. I think this explains some of the difference in interpretation that I still have in discussing these things with some other people. I am going to have to be more careful to both point out the inadequacies of "logic" while at the same time point how how Epicurus uses "logic" himself, as carefully as any of the Stoics or Platonists did -- just like DeWitt observed.
And ultimately that's my best argument against the "absence of pain passages" - that they are logical points being made in the context of refuting the anti-Platonic arguments, but were never intended to represent the full picture of the nature of pleasure any more than geometry or map-making can represent true reality - they are useful for discussing aspects of reality but they aren't reality themselves. So it may be that the "continuity" issue fits in the same category.