I've heard a lot of arguments claiming that vast territories like galaxies and even just solar systems could never be claimed by one faction. But I'm skeptical of this because the argument is really just "too big" and that's rarely ever a good reason to deny anything. I feel like IF factions can remain unified or at least aligned with each other long term and over vast distances (yeah I know it's a BIG if, but bear with me for the sake of this argument) they'd just keep growing incrementally and scaling up their ability to claim new territory. Now, self replicating machines complicate this a bit, but not really since more replicators is better and even a slight difference between factions' resources will get greatly exaggerated over time assuming no paradigm shift in their colonization arms race. Eventually it doesn't matter if a smaller faction sent their probes even a thousand years ahead of time, their enemies will just crush them on arrival. Honestly I think rarher than tons of tiny island factions in a vast universe, you'd get multiple streams of factions that pick a handful of directions and keep expanding out while gradually widening their colonization tendril. Now, that's still enough room for thousands of factions in the near future to expand to the point of claiming galaxy groups, clusters, and maybe a supercluster here and there for the major powers. And the neat thing is this could be largely non-violent as long as probes turn out to be the best way to do things, with citizens obly arriving after a territory has been established and factions (hopefully) wouldn't attack conscious citizens. There might also be plenty of smaller factions right along the borders between tendrils that just barely managed to claim some stuff.