perhaps the leveling itself is linear because the difficulty in sleeping with new people gets logarithmically easier

This is an interesting notion, and, similarly, I feel that figuring out my 30th partner (suddenly I wonder who exactly that was) was much easier than my 3rd (when I was, if not clueless, at least short on clues). But my thinking was not so much about the ease of maneuvering that comes from a developed sensitivity; and here, I make a side remark: I am very disappointed to partake in media where a fling or ONS or sex etc is depicted with something like, two people lock eyes at a bar, they smile at each other, the guy takes a shot, and the next scene opens with them in bed (or maybe she is in bed and he is standing and getting dressed). For the viewer who is not sure how the world truly progresses from across-the-room-eye-contact to clothes-off-bodies-touching, I feel so much is lost in that elision from pre-meeting to post-coital and it is misleading, because, to me, it is the space in between that is of such interest. The awkwardness and is-this-right-phrasing and so forth are, to me, essential to enjoying stranger-sex. I think many opportunities for people to engage in consensual, mutually enjoyable sex are lost because there is a lack of understanding by one or both parties around the ways to engage respectfully in the lead up to a ONS. Anyway, back to the main story.

My thinking frequently adheres to a framework in which one has routines and bursts of novelty; others may call this scripts and improvisation. Some of the routines are really not worth diverging from; a silly example: Looking both ways before crossing the road! You should do that. But there are other areas in which novelty and a break from routine becomes meaningful and shapes one's own life for the better; to me, stranger-sex, sometimes, presents that sort of opportunity. "Varying one's sources of pleasure" is not a radical idea when stated in that generality.

In describing the growth as logarithmic, I mean: the novelty that I once felt in having stranger-sex has long diminished. The ways of introducing novelty that I formulated, which may look a bit like competition with myself, have lost a bit of their luster, too; examples being: have sex within 5 minutes of meeting the person; have sex with a person who you met for the first time between the hours of 10AM and noon; have sex with someone who cannot speak English by seducing them in their own (or a shared) language. But by now, okay, it is perhaps enough, for what novelty is introduced by a new body?

To me, in my feeble dotage (29 and counting), the ephemeral pleasure of a ONS (e.g., coordinated through OKC) may not differ tremendously from what I felt with the last few people whom I encountered just one or a few times. Still, I will delight in the juxtaposition between unknown and knowing, but it is a transition that has become quite familiar to me.

To speak in concrete if crude terms, though: Someone visiting from out of town messaged me late Monday night, and we made plans to have meet up Tuesday to have noontime sex, which I hoped would capture that novelty (names were not exchanged, which is something I have never quite been able to side step, as curiosity gets the best of me). Anyway, she messaged me the next day and said [insert rationale for cancelling though I think it was, succinctly, cold feet] so, that proposition was for naught, but at least I know the idea of a ONS (well, daytime; ODS) still holds some appeal.

This response of mine wended a bit from its intended destination (!) and I will delete it, too.