I just noticed this and I want to comment:
I use natural and necessary or unnecessary as a first step to evaluate a given desire, then I think about whether the various costs involved (pain) will add up to more or less than the resultant pleasure.
I agree that the natural or necessary analysis is a good first step in the analysis, but it's good to remember that there is nothing intrinsically wrong with the pleasures in either of these multiple categories, but because these categories are thumbnail rules for helping us predict the amount of pain that is going to come from the choice, as explained by Torquatus in On Ends.
The point of my posting is to emphasize that this is the starting point of the analysis, not the end point, and not a substitute in itself for the issue of "what will happen" and the eventual result of whether the end is net positive or net negative as to the pleasure/pain balance.
Thumbnail rules are highly useful, but they exist in a larger context that can sometimes be dramatically violated. The goal is to keep your eye on the END, which is pleasure, and never to let any tool (like virtue, or even this system of categories) to take the place of it.