The Orthodox Church has no direct teaching regarding whether these ages are to be taken literally or not. The Church will say that whatever Holy Scripture states is without error, yet must be understood in terms of the conventions of literature that were in use at the time.
It is known that, in many ancient cultures, fantastically long lives were ascribed to famous forebears. Therefore, the ages of Adam, Noah, Abraham, Methuselah, etc. could be a symbolic indication as to the greatness and venerability of the individuals.
On the other hand, we cannot negate the obvious: With God all things are possible. God, therefore, can keep people alive as long as He wants, and if He wanted someone to live to be 900 years old, then that person certainly could have.
Perhaps this is one of the reasons why we are so fond invoking the prayer and singing “Many Years!” to people on special occasions.
