Third generation syndrome

"The "third generation syndrome" is the tendency for third generation Christians to walk away from the faith. The first generation of people saved tend to be enthusiastic and "on fire" for the things of the Lord. The children of the first generation are in church and saved but tend to be less enthusiastic for the things of the Lord. By the third generation many children are typically nominally involved in church, or not involved in the things of God at all, or in worse case scenarios, not even saved."


Is this true?  And if so, why do you think it happens?