The “stars themselves are moving around, so once you settle a nearby system, the star moves you to another part of the galaxy where more new stars will wander by and give you another nearby star to settle
Note: What bakes my noodle is what happens at the end and what i had never considered in these types of thought experiments. This is especially noticeable at the galactic center, where stars are much more densely packed.
Migration ships are launched once every 10,000 years, and no civilization can last longer than 100 million years. Ships can travel no farther than 10 light-years and at speeds no faster than 6.2 miles per second (10 kilometers per second), which is comparable to human probes like the Voyager and New Horizons spacecra
Note: Their constraints are very conservative, to the point that it's basically at or near our technology level: