After they accomplished their primary tasks, they were still going strong and, because of an alignment of planets that occur about once ever 175 years, Uranus and Neptune were put on the schedule and they kept on going.
According to the webpage of the Jet Propulsion Lab:
"Between them, Voyager 1 and 2 would explore all the giant outer planets of our solar system, 48 of their moons, and the unique systems of rings and magnetic fields those planets possess."
Pretty good engineering.
Man has become the dominant creature on the planet (for better or, as we found out yesterday, for worse) in part because our ancestors recognized that they couldn't wrestle a wooly mammoth to the ground, so they would have to either chase it off a cliff or be able to throw something at it - preferably a bunch of somethings with points - that would kill it.
On or about September 12, 2013 Voyager 1 crossed over an invisible line that took it out of the influence of our sun and into what is known as interstellar space; about 11 billion miles away.
If my highly developed interstellar arithmetic, and Einstein's theory of general relatively are correct, at that distance it takes 21 days to get a radio signal from where the Voyager is back to Earth.
Unfortunately it happened during a week when we were consumed with an Op-Ed in the New York Times sent in by Russian President Vladimir Putin and the really crucial issue of Larry Summers' withdrawing from the competition to be the Chairman of the Federal Reserve Board.
From rocks to slingshots to arrows to trebuchets to cannons to rockets we have now flung a man-made object completely out of the solar system.
That's a very big deal and we should be proud of ourselves.
That all those things have happened in the same week demonstrates the yin and the yang of human existence.