The lifespan (either longer human, or mechanical) of individual travellers does not affect the speed of colonisation, so any communication would be quite limite

The lifespan (either longer human, or mechanical) of individual travellers does not affect the speed of colonisation, so any communication would be quite limited. Which means that there be will be no interstellar "empires" or even cultures -- and if any habitable worlds are as rare as it seems to be the case for us, I'm not very optimistic about encountering any alien species any time soon.