I would guess that arbitrarily large but finite (extended) brains are much less realistic than infinite universes, though. I’d put a probability <1% on arbitrarily large brains being possible, but probability >80% on the universe being infinite. So, maybe actual infinities can make do with more conservative assumptions than the particular money pump argument in my post (but not necessarily unboundedness in general).
I would guess that arbitrarily large but finite (extended) brains are much less realistic than infinite universes, though. I’d put a probability <1% on arbitrarily large brains being possible, but probability >80% on the universe being infinite. So, maybe actual infinities can make do with more conservative assumptions than the particular money pump argument in my post (but not necessarily unboundedness in general).