'Eighty' in the Bible

And Barzillai was very aged, eighty years old; and it was he that had maintained the king while he abode at Mahanaim; for he was a very great man.

I am this day eighty years old: can I discern between good and bad? can thy servant taste what I eat and what I drink? can I hear any more the voice of singing men and singing women? and why should thy servant be yet a burden to my lord the king?