"I like you a lot. You make me happy. But there's probably at least tens of thousands of people in the world that can provide me with what you're providing me. So you're replaceable, and if we broke up, I'd get over it after a few days/weeks and find someone else.

Mr. Zerner, a problem with your counter-argument is that you aren't actually going to meet the tens of thousands of hypothetical people who could satisfy all the same desires and needs as a current romantic partner is meeting. You won't even meet one hundred, or, like, thirty. If you're lucky, you could meet a dozen other people who satisfy you romantically as much as any one romantic partner you loved the most satisfied you. . You could take an approach of shallowly connecting with as many women you think are very compatible with you as you can find. However, unless you're some Casanova, that seems like a poor strategy for creating a loving relationship, or several of them (rapidly). So, that doesn't seem like a sound argument for "sorry, my darling, but you're replaceable". I believe this would hold true for almost everyone who would make this case.

Also, it doesn't seem like you qualify how much you (would) love a given significant other. Depending on how much value the person brought into your life, it could take months, or even years, to overcome the loss of their companionship, rather than days, or weeks. It could also take you that long to find someone to replace her with, who provides just as much value to your life. I could generalizing too much from the example of my own experience, but it's the rare person who replaces the most significant romantic partner they've had previously with another in the span of only a few weeks, or a couple of months. I wouldn't be surprised that some people are quicker, or better, at this task, than the average. So, Mr. Zerner, unless you have great reason to believe you're above-average in this regard, don't discount the expected costs of finding a new partner so much.

Also, I do like you and care about you (more than a big majority of things), but not nearly as much as I do about myself. And not nearly as much as I do about knowledge, understanding, and my ambitions. So I might get obsessed about these things, stop caring about you as much, and consequently, break up with you. In fact, there's a lot I'm confused about and for that reason, I can't make anything close to a commitment. I don't know if I should be trying to be happy, being an effective altruist, combatting death, or trying to seek knowledge and understanding of the world we live in.

You're signaling that you have ambitions in life which are more praiseworthy, or laudable, or of a higher caliber, than just pursuing purely selfish ends. You're explaining to a hypothetical romantic partner what else you want to do in life. It seems like you're also trying to explain that to us as readers as well. The way you're asking if love is a 'good idea' seems to be about if committing all the time and effort to something like marriage would require is worth the opportunity cost of not being able to spend that time and effort (trying) to save the world.

I'm suspecting you're asking "how do I balance a commitment to such a lifestyle, while still appearing and being normal enough to do (many of) the typical things typical humans do to be happy?" I suspect you're asking these questions, not only in the interest of playing out an argument, but because, probably judiciously so, you don't have a 'gung-ho', confident solution to this personal conundrum.

You're not the only person with such concerns. I'm a nerd interested in saving the world while being awesome as well. I have similar concerns about committing too much to a single person, or to my family, at the expense of saving thousands of other lives, or whatever. Your concerns are shared by others in this community, and we don't have all the answers. It seems that other folks 'well on their way' to saving the world have encountered this problem as well, yet they haven't given up on making commitments to love others, or without giving up other things which don't broadly benefit others. We could learn much from them.

Ideally, I would prefer that the practical conclusions resulting from discussions on Less Wrong could generalize to, and be implemented within, as many of its readers' lives as possible. So, I don't mean for this response to be critical of your personality, and I hope me raising these points hasn't offended you. I believe it would be better if you were to clarify what your true concern here is though,, and summon the gumption to address it to us more directly. This is because we could have a clearer discussion, that benefits, and interests, more of us.

they stop being strategic because they stop considering alternatives to the monogamous relationship they have with their SO. None of this seems rational to me.

Maybe you really will need a significant other to rely on you less, lest they meet stringent conditions, or you cannot commit to them deeply. A small minority of people who commit themselves greatly to a cause are capable of that. It seems most people don't, not because they hate the idea, but because forgoing strong social bonds that most everyone else acquires makes them miserable. So, maybe loving someone so much seems irrational when that effort could be spent on other ideas which seem so much more valuable, on paper, than just loving one person.

We can discuss committing to both personally love others, and to making great accomplishments. That seems like a different discussion than this one, though.

Note: edited for brevity.