[sandgiant]

There is a sort of philosophical upper bound on the total size of the Universe in an eternal-inflation scenario. This is the Boltzmann brain paradox. The argument goes that if there are infinitely many universes it is infinitely more likely for you to be a brain randomly fluctuating into existence in the vacuum, rather than being an actual human being evolved through evolution.

This conclusion is obviously absurd, so the argument goes that there can't be infinitely many places in which random things can happen in the Universe. Note that the size of the Universe required to produce a Boltzman brain is much larger than that discussed in the article. It's still nice to think that there might be an upper bound for us to avoid some of the more daunting implications of the anthropic principle.