7 There is also something like this in this present life, and besides that solution of the parable, by which they who were called at the first hour are understood of Abel and the righteous men of his age, and they at the third, of Abraham and the righteous men of his age, and they at the sixth, of Moses and Aaron and the righteous men of their age, and they at the eleventh, as in the end of the world, of all Christians; besides this solution of the parable, the parable may be seen to have an explanation in respect even of this present life. For they are as it were called at the first hour, who begin to be Christians fresh from their mother's womb; boys are called as it were at the third, young men at the sixth, they who are verging toward old age, at the ninth hour, and they who are called as if at the eleventh hour, are they who are altogether decrepit; yet all these are to receive the one and the same denarius of eternal life.
Source: Sermons on Selected Lessons of the New Testament (New Advent)