NASA doesn't push that line. They say the primary mission is X flights or whatever. When the probe lasts longer reporters translate that into "designed to only

NASA doesn't push that line. They say the primary mission is X flights or whatever. When the probe lasts longer reporters translate that into "designed to only last X flights!!1!" NASA never wants to say a probe will probably last longer than its primary mission because then reporters go the complete opposite direction and claim NASA said a "probe failed to last the claimed X+Y flights".