NASA’s Mars helicopter is somehow still flying

Obviously the flip side is that some probes will fail.

I expect they are not operating at the most efficient use of capital (if measured in probe lifetime/$). But since they are funded by the government, the politics mean that failure, even within expectations, would result in reduced funding.

So maybe this overbuilding is a symptom of government inefficiency?

If you want a 95% probability of 90 days, you also get something like a (pulling numbers out of thin air) 75% probability of a year.

Meanwhile, there's a academic research politics side going on, where a lot of people want their experiment to be done by your probe, the negotiations for which happen oftentimes before the probe has a solid design. You want to be able to tell some subset of people "as long as we don't screw up terribly, you should be safe betting on this", and tell the others "you'll be in the "nice-to-have" category, don't get your hopes up". So a mission lifetime gets decided, pretty much independently of engineering considerations.

They could, in theory, update their lifetime estimates after the project is finished, but there is little to gain at that point: The researchers with experiments in the "nice-to-have" set have already hedged their bets, the engineers would rather have a 50x success than have announced an over-estimate, and nobody really complains when the Opportunity is still truckin' around the Martian surface years later.

"It’s absolutely ridiculous,” Tzanetos said. “This is a once-in-a-lifetime kind of thing.”