'Eighty' in the Bible

Now Barzillai was a very old man, as much as eighty years old: and he had given the king everything he had need of, while he was at Mahanaim, for he was a very great man.

I am now eighty years old: good and bad are the same to me; have meat and drink any taste for me now? am I able to take pleasure in the voices of men or women in song? why then am I to be a trouble to my lord the king?