How long does it take to lose a culture, from a Christian perspective?
Actually, it takes only one generation.
The devil knows this, and of course God warns us about it. Adolf Hitler understood this when he said, "He alone, who owns the youth, gains the future!"
Over and over again in Scripture, God instructs His people to make sure they train up the next generation.
For instance, when God miraculously enabled Joshua to lead the people through the Jordan River, the first thing He told Joshua to do was to take twelve stones from the riverbed to build a memorial. But what was the memorial for?
Joshua explained, "When your children ask their fathers in time to come, saying, 'What are these stones?' then you shall let your children know ... the Lord your God dried up the waters of the Jordan before you until you had crossed over ... that all the peoples of the earth may know the hand of the Lord, that it is mighty, that you may fear the Lord your God forever" (Joshua 4:21–24).
The stones were to remind the parents to make sure they taught the next generation about the true God. They were instructed to pass on the knowledge and fear of God to their children.
I think one of the saddest pages in the Bible is in Judges 2:10–12, "When all that generation had been gathered to their fathers, another generation arose after them who did not know the Lord nor the work which He had done for Israel. Then the children of Israel ... forsook the Lord God of their fathers, who had brought them out of the land of Egypt; and they followed other gods from among the gods of the people who were all around them."
After Joshua and all the first generation of parents who entered the Promised Land died, the next generation served false gods! It took only one generation to lose the spiritual legacy that should have been passed on.
[Read the rest of the article at Answers in Genesis.]