'Eighty' in the Bible

Barzillai was a very old man, eighty years old; and he had provided the king with food while he stayed at Mahanaim, for he was a very great and wealthy man.

I am this day eighty years old. Can I [be useful to advise you to] discern between good and bad? Can your servant taste what I eat or drink? Can I still hear the voices of singing men and women? Why then should your servant be an added burden to my lord the king?