Commentaries:
How long is forever in this case, when we are talking about human beings? A human being cannot serve another human being any longer than he lives. A definition begins to arise for how the Bible uses the term. Biblically, forever means "as long as the factors which set the conditions exist."
In Exodus 12:14, 17, and in the Festival chapter, Leviticus 23:14, 21, 31, and 41, forever, in reference to the holy days, is for as long as "your generations." Are the generations of Israel still continuing? Indeed they are.
John W. Ritenbaugh
The Covenants, Grace, and Law (Part Nineteen)