'Eighty' in the Bible

Now Barzillai was a very aged man, even eighty years old: and he had provided the king with sustenance while he lay at Mahanaim; for he was a very great man.

I am this day eighty years old. Can I discern between good and bad? Can your servant taste what I eat or what I drink? Can I hear any more the voice of singing men and singing women? Why then should your servant be yet a burden to my lord the king?