Even more impressive is the Opportunity rover which landed on Mars in 2004 and is still active. It’s now something like ten years beyond its planned mission life and has traveled 26+ miles on the surface.
Would that all government programs had such a return on investment (ROI)! However, this project is not the champ for ROI, that honor belongs to Voyager 2, the spacecraft launched 16 days before its twin, Voyager 1. Still reporting back to JPL/NASA, its current flight time (12/15/15) is 38 years 3 Months and counting.
These are the "Golden Record" probes of Carl Sagan fame. Both are entering true Interstellar space where they are beyond the immediate influence of our star, Sol. V2 is reporting back on a weekly basis and is expected to continue for about another 9 years.
We always remember the ones that fail, the wildly successful ones are ignored.