At this point in the conversation I would point back to Rolf's original question:
I can acknowledge that I enjoy unnecessary pleasures and wish to pursue them, but logically speaking, why exactly should we not aim to fulfil only our necessary desires?
Titus and Godfrey, in your answers, did you address this question specifically? Do you agree that you can pursue only necessary pleasures and reach 100% pleasure (or happiness)? If you can pursue only necessary pleasures and reach the target, why would you pursue any others than those which are easiest to obtain?
I know Cassius' is fighting the image of the minimalist frugal Epicurean who lives on bread and water but I would like to see more sensitivity as to why there is a category of"unnecessary desires" in the first place.
I think that's a good question, and to make it even broader, why does any part of this categorization exist in the first place? Is it a logical part of explaining "the nature of things" like atomism or a position on gods or life after death or that pleasure is the goal of life? Or is it a "tool" question such as the analysis of virtue, to be applied properly only after the others are adequately understood?
I can definitely see that there are many people who are convinced that reckless pursuit of power and fame and riches who need to revise their goals so as to drop those which are most destructive to them. But while we are helping them see the right way to approach that question, we need to avoid stating things in a loose way that is logically confusing to those who are closely trying to follow the logical consistency of the philosophy. We shouldn't fight our way out of claims of supernatural or absolute right and wrong only to turn around and fall victim to interpretations that there is a strict list of "natural" and "necessary" that applies to everyone.
Many of us have observed before that what is "necessary" and "natural" in one time and place is totally unnecessary and (again depending on your definition) unnatural in another.
So I suppose what I am saying ultimately is that the full explanation of the natural and necessary approach must include the observation that natural and necessary are relative to time and place and other circumstances, and are not to be interpretation as a call to absolute frugalism/minimalism. And that's how I read the Torquatus explanation, which points to the "principle of the classification" (some things are harder to get than others) as being the important thing) rather than assigning a specific absolute meaning to any category.