Major Themes In Miniature

"Instant communications unified planets; but the days and weeks and months between stars let their systems drift culturally apart - let hell brew for years, unnoticed till it boiled over - made a slow growth of feudalism, within the Imperial structure itself, inevitable. Of course, that would give civilization something to fall back on when the Long Night finally came."
-"The Game of Glory," II, p. 308. (For full reference, see here.)

Four recurrent themes of the Technic History:

no instantaneous interstellar communication;
hell brewing over (also in the interstellar period of the Psychotechnic History);
growth of feudalism within the Empire;
something to fall back on when the Long Night comes.

This story returns to the fourth theme at the end when Flandry says:

"'I'd like to have Nyanza well populated. When the Long Night comes for Terra, somebody will have to carry on. It might as well be you.'" (p. 339)

There is instantaneous interstellar communication in Anderson's later novel, For Love And Glory, although I find the idea implausible. The master of instantaneous communication in sf was James Blish: see The Dirac Transmitter.