If Lucretius was deciding between spending a life as a shepherd or spending it writing didactic poetry, how would intensity, duration and duration apply? I tend to think of this breakdown in terms of maximizing overall pleasure. In this case:
In thinking more about your intensity, duration, and location schema, it seems Epicurus himself endorses your idea of applying time/duration to pleasure and how we make our choices:
Quote from Letter to HerodotusWe must chiefly reflect upon that to which ***we attach this peculiar character of time***, and by which we measure it. [73] No further proof is required : we have only to reflect that we attach the attribute of time to days and nights and their parts, and likewise to feelings of pleasure and pain and to neutral states, to states of movement and states of rest, conceiving a peculiar accident of these to be this very characteristic which we express by the word `time.' [He says this both in the second book "On Nature" and in the Larger Epitome.]
So, Epicurus states that we DO apply the characteristic of "time" to the feelings of pleasure and pain and to neutral states, to states of movement and states of rest (δὲ καὶ τοῖς πάθεσι καὶ ταῖς ἀπαθείαις, καὶ κινήσεσι καὶ στάσεσιν). Now, I'm not sure what we are to glean from the translation referring to a "neutral state" ἀπαθείαις (apatheiais) because that's not one of the two feelings of pleasure: κινήσεσι and στάσεσιν. But that might have to wait for another thread. What I wanted to point out that your duration criteria does appear to have a precedent from Epicurus himself.