Seems like AT flip-flopped on this matter similar to him flip-flopping on Tenshinhan and Lunch. Either way, this is more recent seeing as it came after Super was serialized, and it says:
"Their [natural] lifespan in itself is longer than humans’, but since they are a warrior race, many of them die in battle, and their average lifespan isn’t all that long."
If I were to try and make sense of them both, I would just rationalize it as Saiyans living longer due to only aging significantly after the age of 80, but not having significantly longer lifespans overall due to deaths by battle.