One thing that I have thought about a few times is not just the time scale but also the technological advancement and where we might sit in that continuum. For

One thing that I have thought about a few times is not just the time scale but also the technological advancement and where we might sit in that continuum. For example, spread spectrum radio technology that is used for some wireless communications would be virtually impossible for us to detect even a couple of decades ago. So even efforts like SETI may not see anything because you would have to focus in on one of the habitable planets, at the moment in time when they are using the type of radio technologies we know of, in the spectrum we are looking at. It is possible that there are technologically advanced civilizations out there but they moved past radio and are using something more advanced like quantum entanglement modulation or something we don't yet have the technology to decode. If there is a Galactic Internet, it is probably not based on the modulation of electromagnetic radiation which is limited to the speed of light.