You&#x27;re ignoring constant factors. Space empires will likely expand much faster than dictated by population needs, to the degree that, as it spreads out, it will presumably experience a reduction in population density. Sure, with multiple star-faring empires, there may be a limit to how far in space a given empire can expand, but a Type III society is capable of building all sorts of gigastructures, including ringworlds and dyson spheres, so even a moderate expansion out of a single solar system will provide plenty of room for population expansion. It&#x27;s also likely that immortal or long-lived species will end up having a relatively low number of children (given effective immortality and complete control over reproductive capability, it seems likely that aliens will choose to have a low number of children over their lifetime and will likely wait much longer before having their first child, which means even a simple doubling in population will take place over a relatively long time).<p>Given these reasonable assumptions, it seems likely to me that most space-faring civilizations of this level of technology will never experience any kind of pressure on living space. If you&#x27;ve ever read the Culture series (by Iain M. Banks) then you might reasonably expect such a civilization to &quot;Sublime&quot; before running out of space. Or to eventually alter themselves so as to remove the desire to procreate in a deliberate move to &quot;retire&quot; from the galactic stage.<p>I said &quot;most&quot; because there is of course the possibility that some species comes along that has the urge not just to procreate but to have as many children as possible as fast as possible, and manages to achieve this level of technology without ever altering this behavior. Such a species that is driven to expand its population as fast as possible may then experience restrictions on living space, but such a species would eventually have to enact population control, which could take the form of altering themselves to remove this urge to procreate as fast as possible and therefore will become just like &quot;most space-faring civilizations&quot;.