Again, when parents live as they should it gives their children an excellent example to follow. So often parents blame the bad behavior of their children on the children themselves or the world's influence around them, or anything else but themselves! But bad behavior in the kids often happens because there is bad behavior in the home. And I don't mean poor morals from their parents. There's something else that is far more often the cause: poor examples in spiritual leadership. If Dad and Mom are not regular in their personal time in prayer and the Word of God they fail to lead their children in finding the source of spiritual and moral strength: fellowship with God and the power of God's Word! Now, more to be said about this in the future.
Note that Paul emphasizes the promise in the 5th Commandment. When parents live right and teach right, by their words and their lives, they're giving their children a solid reason for honoring them.. And when kids do what God says in showing that honor God blesses their lives. Long life doesn't always mean "length of time" but more importantly "quality of life." A child who watches their godly parents and honors them by living like them will find their lives fulfilling and satisfying and will be a joy to their moms and dads.