I know people that work in companies that design chips. Those manufacturing cycles are MUCH longer and expensive - you can't just recompile when you test and find a bug. This, their QA is probably more like 10 people doing simulation (behvioral, thermal, timing, power, emissions, RF susspetabiliy, etc) before a design is even fabricated.
I would imagine that in Space Exploration - this would go even higher - given the time and expense of these missions. The point is - saying "it's just software" doesn't help you here. Software is *very* complex and the intricacies of advanced logic, variability of factors - trying to do this stuff probably dwarfs that of the hardware components in this day and age.