Nick Bostrom wouldn't have missed that, he's a very precise philosopher (I'm reading his book Anthropic Bias, and damn I'm glad I didn't have to tease out that

Nick Bostrom wouldn't have missed that, he's a very precise philosopher (I'm reading his book Anthropic Bias, and damn I'm glad I didn't have to tease out that mess by myself). This quote comes from a particular thought experiment. As I'm sure you'll grant, thought experiments don't discuss what to do if that exact hypothetical were reality, they only discuss what attitude to take towards this whole category of situations. In concrete terms yes, some humongously big number of lives are lost every second, more than 10E29 of them, if time travel is possible or creating new universes is possible, but that doesn't change the conclusion. And you miss two things as far as I can see: achieving immortality for yourself is not the maximal good, since for one thing it would clearly be even better to achieve immortality for everyone. Second, you're equating infinities. It's hard for humans to reason about infinities, but mathematicians have in fact described that there are infinities of different orders: you can still speak of some "infinite" quantities as being greater than other "infinite" quantities. It's easier if you just drop the word in favour of "zillion" and reason intuitively about that.