I've also seen it argued that if you get enough future humans spread around the galaxy and into the future it doesn't matter what the discount rate is, their va

I've also seen it argued that if you get enough future humans spread around the galaxy and into the future it doesn't matter what the discount rate is, their value in aggregate can still positive. This is true in a trivial sense, but if I'm not discounting the lives of hypothetical transhumans orbiting Alpha Centurai eleven centuries from now down to zero, maybe I shouldn't discount down to zero the value of other purely hypothetical lives (or "lives") such as infinite copies of a self-aware general AI system trained on twenty-first century human ethics or the long-lived and trouble-free existence of my grandchildren as AI pets either... Seven billion (or even a couple of million) humans in the world today are obviously a sufficient rationale to pay attention to existential threats or stuff that could blow up in our faces including pandemics, climate changes and AI systems, but proponents of actions with apparently vanishingly small probabilities of improving safety tend to need to invoke gazillions to justify prioritising them over tangible solutions to the problems of millions in Bayesian/utilitarian framework.