Maintaining a interstellar empire would require a different way of handling logistics.

My theory is that instead of sending out one ship for a trip at a time, you have to keep a constant stream of ships "checking" on vassal systems. One ship every two months is sent off to the vassal star system to occupy it. Ships make return trips, and as one ship leaves the people subjugated would see another ship come by.

Of course that would mean A LOT of spaceships, but seeing how much material there is in space I have no doubt it could be pulled off. By having a constant line of ships going to a vassal star system would could maintain a interstellar empire of up to a couple dozen star systems.

And as for time and age… Well, there's hibernation, video games and simply changing people's perception of time combined with longer natural life spans. Or hell why even assume the humans haven't become mind uploaded immortal beings by than? I can think of tons of potential technologies used to make the issue of "time" moot for the travelers. 

The people on the planets on the other hand, I have no clue. I don't think technology will constantly innovate rapidly, in fact I speculate it could stagnate in the interstellar age. 

[quote=Kadaeux]
Stealth is impossible in space. Not difficult. Not challenging. Not an engineering problem. Impossible.http://www.projectrho.com/public_html/rocket/spacewardetect.phpSkip straight to "there ain't no stealth in space, do not pass Alpha Centauri, do not collect 200 Spacebucks." :p
[/quote]

Thankfully the sheer vastness of space, the inability to bend light and presumed advancements in intercepting projectile attacks means stealth isn't that necessary anyways.

Keep moving, keep firing, and always change direction seems to be the way you play the space game. Stop too long and the enemy gets the edge.

But I don't really know, I just speculate based on what arguments I hear and listen to those that sound most convincing.