Works for Me...

Forty years.
Why did God make Moses and his Jews wander around in the desert for forty years?  Why not twenty? Why not fifty?

What happens in forty years. anyway?
People die, that's what.  Two generations die.
In forty years, God knew that virtually none of the people who He rescued from Egypt would still be alive.  None of the ones who worshiped the golden calf.  None of the ones who complained about not having onions.  None of them, not even the babies.

 Your sons shall be shepherds for forty years in the wilderness, and they will suffer for your unfaithfulness, until your corpses lie in the wilderness.--Numbers 14:33

After forty years, none of those Jews still living would have remembered anything about their life in Egypt.  They all would have grown up in the desert.  They would know nothing of lush harvests or emerald rivers.  They would know only sand and sun and manna and God.  And they would be grateful for the promised land.

God thinks in terms of generations. Men do not.
Even Hezekiah, who came to know God and to teach his whole kingdom about Him, didn't get that God does not just care about individuals.  He cares about legacies.

 Then Isaiah said to Hezekiah, “Hear the word of the Lord Almighty: The time will surely come when everything in your palace, and all that your fathers have stored up until this day, will be carried off to Babylon. Nothing will be left, says the Lord. And some of your descendants, your own flesh and blood who will be born to you, will be taken away, and they will become eunuchs in the palace of the king of Babylon.”

“The word of the Lord you have spoken is good,” Hezekiah replied. For he thought, “There will be peace and security in my lifetime.”--Isaiah 39:5-8 

In other words, Hezehiah thought, "It may suck to be you, but it works for me..."

God doesn't agree.

What damage does generational faithlessness produce?

Examine your own heritage. 

What did your grandparents do or know that has been lost?

Did a grandparent build or sing or sew or cook something that has disappeared forever?

Did they know how to survive without car or grocery store or telephone?

Does they have a heritage of faith that has dwindled from misuse?

Two generations and it is lost.  Gone, and irretrievable.

Forfeiting what was good from prior generations steals from our children.

We keep the faith of our fathers today not just because it benefits ourselves, but so that we can build an unbroken chain of those who know and love God for the future.

And you shall teach them your children, speaking of them when you sit in your house,
and when you walk by the way, when you lie down, and when you rise up.--Deuteronomy 11:19