There are many interesting points made here by Cassius, Godfrey, Don.
It seems to me that you can look at pleasure and pain as either additive or subtractive. So the subtractive way to look at pleasure, is that pain has been removed, and in it's place we now have pleasure. And since Epicurus says there is no neutral state of feelings, then that would mean that (for example) the pleasure of fun and entertainments has removed the pain of boredom.
It is more appealing to me to see pleasure as additive, and that is probably a heuristic. However, if one is to maximize enjoyment, then it is good to remove mental pains of anxiety and stress.
I'll need to ponder the jelly bean jar analogy a bit more to see if it works for me, or come up with something that can also accommodate the two types of pleasures - pleasures that last only a short time and pleasures that last much longer.