Faster arrival
As the New Horizons team studies the mission and their launch window, they realize that they can get the probe to Pluto a year earlier than anticipated.
This [is] a great opportunity to improve our scientific return while reducing mission risks and costs. We’ll get a better look at Pluto itself, since more of the surface will be sunlit and the atmosphere will be another year away from freezing onto the planet’s surface. We’ll have more fuel for the journey into the Kuiper Belt after exploring Pluto-Charon, and the shorter cruise time reduces some of the costs associated with flight operations.