Another good reason for leaving the solar system completely is, the Milky Way and Andromeda galaxies are plunging toward each other and are destined to merge.
When this happens, a good number of stars will be thrown into the core of the new galaxy, where there will be a rash of large star formation followed by a long string of close-proximity supernovas. If our star is one of the ones thrown into the core, we will not want to tag along on that journey.
Another good number of stars will be ejected into intergalactic space. Some will stay clumped together near the galaxy (the Magellanic Clouds are examples of this having happened in the past). Some stars will end up alone in the void.
Ending up in a new Magellanic Cloud might not be so bad, but being alone in the void will be a problem. When it's time to move to a different star system, it will be helpful if there are nearby star systems.
It will be good if humanity is not still tied to our existing star system by the time the merger happens, but is free to move elsewhere as necessary.
After the merger we can find a nice quiet red dwarf with a 10 trillion year lifespan and settle around that.