When the airplane flies 580 days where it previously flew 570, I do not assume the 10 extra days are due to some marginal improvement, just to the fact they kept the mission going longer. The 5th airplane could presumably have made it to 580 days too if the mission team had wanted that.

Bolt is amazing because he does something every time that you are certain he couldn’t do before (unless he was deliberately slowing down, which doesn’t seem like a winning strategy).