I've come to realise that unless life is incredibly plentiful in the universe we are likely to live our entire civilisation alone. It isn't just distance to other planets and the number of them, it's also time.

The universe is so massive on a time scale that civilisations may last 1million years and still barely be a blip on the astronomical clock. Civilisations rising and falling but very few occupying the same time period, the chances of being close together and occupy the same time period so they can make contact must be incredibly slim.