Intergenerational Friendship: Ubiquitous in Imperial society, given both how very long lifespan is compared to generation (any given generation is a small demographic segment indeed, and therefore… and besides, after the first century or so, does it really matter?).

And also the low birthrate mentioned under Immortal Procreation Clause meaning that if you’re the kid in town, chances are that you’re the kid in town.  Children socialize with older generations because that’s the only socialization going on.