[chmike]

Agree. A space-faring civilization would have space ships perfectly adapted to their need for sustainability, and they can move to avoid any danger. We can also assume that well advanced civilization have mastered transmutation and that they might need access to planets only to get matter they can transform in whatever they need.

The motivation for traveling in space can only be to decrease probability of extinction and to increase their knowledge. The later may include studying other life forms and what they have learned. As a consequence, I assume they would specifically target solar systems with a high probability to host well advanced life forms. I don't give much credit to a random expansion in the milky way.

Regarding the Fermi paradox, the only paradox is excluding the UFO phenomenon as possible extraterrestrial manifestation.