One reason to plan on colonizing elsewhere before our 5 billion years are up: asteroid collisions.

Neil deGrasse Tyson discussed the threat of asteroid impact on StarTalk Radio (emphasis ours):

We know the size of an asteroid that would do very bad things. It’s about a kilometer across, little more than half a mile across. That size asteroid would disrupt civilization. It wouldn’t leave us extinct, but it would disrupt the food chain, transportation channels, things that we rely on for modern living.

…And then at a ten-kilometer size, you’ve got about an extinction level asteroid.

…In the old days, we thought it would just leave a crater, and [you’d be affected only] if you were unlucky enough to be where the crater hit…but we learned that the stuff it thrusts into the atmosphere blocks the sun, cloaks the earth, knocks out the base of the food chain — because photosynthesis can’t unfold — and a wave of extinction percolates across the tree of life.

Check out NASA’s map of Potentially Hazardous Asteroids or dig into more data at the Near Earth Object program. You may have previously heard NdGT describe the impact risk from Apophis, a 0.325 kilometer-sized object, whose risk of impact was of concern in 2013 but later downgraded.