With that said, my perspective as a former NASA insider is that JPL is known for the exact opposite, underperforming and overdelivering.
I mean, they have a nearly perfect track record of mission success (sorry Beagle) and when the missions do succeed they often persist for many times over the original lifetime requirement.
Additionally, and yes this is a vast oversimplification, if you just look generally at space exploration missions, they are far more prolific than any other NASA center.