In listening to this over today here's something I'd like to explore:
In the sections where Lucretius is talking about people not realizing the "limits of possession" (I need to find the quote) I wonder if th4re is not another shade of meaning rather than the "limit" referring to "how much is possible."
Don't some of the words for "limit" have the additional connotation of the "goal" or "target" of a thing?
In the context of discussing the "limit of possessions" I would think it would be more natural for them to be saying that people don't keep in mind the REASON FOR WHICH they pursue possessions in the first place. To me, the issue is not that people forget or don't think about calculating the optimum amount of possessions, as if there is some magic quantity -- they forget the "target" or the "goal" or the reason for having possessions in the first place -- which is pleasure. To me that makes it easier to understand the point - that you calculate the optimum amount of possessions to pursue purely by reference to whether the amount of your possessions optimizes your pleasures.
Which is closely parallel to how you judge the "virtues" or any other "tool" (which is what possessions are) - you calculate the optimum amount or even whether a thing is desirable or not by looking to the purpose for choosing in it or engaging in it. You're really not so much worried most of the time whether you are actually AT the "maximum extent" of a thing but whether it is helping you make progress toward that target.
And of course all this reminds me that the word "limit" as it is used fairly regularly in Epicurean texts is not a word that we today may be construing in the same way as they would. It seems to me that your normal ordinary person ALWAYS thinks of "limit" as "cap" or a "maximum" or a "restraint" - all words that have negative connotations. We don't normally use it today to mean the second definition here of "the utmost extent"
It would be interesting to look into the Greek and Latin words being used when our translators use "limit" to see if there are shades of meaning that might be helpful to explore.
NOTE: OK I see that in the Latin that is translated limit of possession what we have is FINIS - which is easier to see as "the END" in the sense of "the end of the activity is to achieve ______"
nimirum quia non cognovit quae sit habendi finis et omnino quoad crescat vera voluptas....