How far could a spaceship go if we never ran out of thrust? (2020)
Say you take the one-way ticket to travel to a far off galaxy at 1g acceleration to go mine space-diamonds...What when someone else in a few hundred earth years invents the 1.1g rocket to go mine those same space diamonds?   They will arrive millions of (local) years before you.   By the time you arrive, the space diamonds will be all mined and you'll be seen as a cave man.That reason alone means it's never worth departing on a long journey, because someone else always has an incentive to overtake you and get there millions of years sooner.