Any life form that can (a) divorce its intelligence from its physical substrate, and (b) forge a sustainable energy relationship with one or more stars, has the capacity to be very, very long-lived. I think if there exist aliens that we are capable of finding, they will be in the form of slow-moving, slow-spreading "Space Ents", beings who are perfectly content to send SYN/ACK messages with 500,000 year ping times. Play out natural selection in the ginormous sandbox that is Universe, and I think that's the only inevitable outcome (barring FTL).
Almost. Wanderlust. The ebb and flow of disaster and recovery. A pond overflows, a forest burns, a volcano erupts, a comet hits Earth. We always send out the scouting parties and come back. There is no immediate economic logic, just the 1 billion old instinct to check out the next habitat. By Tyma's cold logic, there is no point in tourism, yet we spend 10% of our global resources for an utterly useless activity. Why?
Still the argument "they have their ships therefore they don't need our Earth" is more than shaky. I concur with Hawking: we can definitely imagine aliens who wouldn't blink an eye before they won't care for life of humans, the same way we eat other animals or simply destroy them as the side effect of doing something for us more important.
True we would not be important, but at least we would know we are not alone.