> Initially designed to last five years NASA tech often seems to outlive its initial mission length by a massive margin. The Mars rovers spring to mind. It's incredibly impressive, and almost embarrassing! Surely this isn't accidental. Is the kit massively over-specced? Do the uncertainties and risks necessitate such a depth of redundancy that when stuff goes kinda smoothly the thing lasts 9 times longer than it was…
There is certainly a political element, when they tried doing cheaper missions they had two failures in a row which was really embarassing, even though probably if they had stuck with it it would have still worked out cheaper than using the low risk approach.
Mainly though if you design a spacecraft to have a 99% chance of lasting five years it ends up with a pretty high chance of lasting 30 years.