The writer Gigi Love doesn't sound at all constrained or hemmed in or regretful about commitment to one person (perhaps 1+) in the future, it doesn't sound like they have any pregrets about missed opportunities in the future, a kind of soudade — nostalgia for something that has not and will not come to pass, or a place you’ve never been. Which all seems very healthy.
That is contrast with those, who on the eve of a commitment, become anxious about the missed opportunities in the future, perhaps because of some complicated belief in monogamy, commitment, till-death-do-us-part of marriage combined with doubt about whether “this one is the one", whether they are settling. (There was a couple I knew: the guy wanted to have "one last adventure" before some envisioned boredom of marriage, told his fiancee he didn't want her along and went backpacking for a month with his buddy instead. The fiancee stayed back and had sex with me instead.)
So, how many or how much or what breadth of experience would be enough? I imagine there are quite a few people, a sizable fraction of adults, who feel they haven't had enough, can never have enough -- other than perhaps those with a low sex drive, a commitment to other causes, those who are externally pressured by religion or morality into some weird repression, or those lucky few who've had a community and opportunities to match their sex drive. I imagine that even in the Bay Area ethically non-monogamous, polyamorous community there are some who might regret "the one (or three) that got away". There is always some imaginable experience you haven't had, or one that someone else has actualized but you haven't - a one-night stand threesome on a beach with the couple of news-anchors you met on the dance floor ...
Here are two questions which have helped me figure it out:
Q1. Can you imagine having better sex with someone else (not more or different, just "better", whatever that means to you)? (No.) Are you satisfied with the idea of only having sex with this person for the next 'x' years, that whatever you want to explore you will be thrilled to do so with them? (Yes.)
Q2. Have you had sex you've regretted - a one-night stand where you've had to fake desire, had one foot on the floor, were turned off by some aspect, where they were turned off by you, turned their face away? (Yes.)
This second question is the one most people don't give enough importance to - do you have enough negatives in your training data set? Why is this important? Because a single point doesn't allow you to calibrate your experiences, you won't have an idea of the spectrum of experiences if all your experiences have been middling or positive. If you don't know how bad it could be you don't have enough data to evaluate how much better than middling your best is.