There are some questions to which only God has the answer (Deuteronomy 29:29).  The list of the human ancestors of Jesus Christ spanned about 2000 years from Abraham, and we do not know why it was so long (and neither longer nor shorter).  Interestingly, these verses tell us that there were 14 generations in about 1000 years from Abraham to David, giving an average generational age of just over 70 years; but 14 generations in about 500 years from David to the exile and another 14 generations in around 500 years to the birth of Jesus Christ (giving an average generation span of about 35 years).

We do not know why that occurred.  But we do know that even during David’s rule, God's law became distorted and ignored, and family feuds added to the instability of the nation's leadership.  David’s son, Amnon, raped his half-sister Tamar leading to her brother, Absalom, killing Amnon (2 Samuel 13:1-29).  Later, Absalom led a rebellion against David resulting in civil war (2 Samuel 15:1-14) which set the scene for the eventual break up of Israel into two kingdoms (2 Chronicles 10:12-19).

Absalom’s rebellion broke the fifth commandment (along with all the others): "Honour your father and your mother, so that you may live long in the land the Lord your God is giving you." (Exodus 20:12)  The privilege of longevity was curtailed.  And without God at the centre of life, it is numbingly meaningless … as Solomon experienced (Ecclesiastes 1:2).  And after the exile too: instead of responding to God in faith and obedience, they soon went their own way; and for 400 years there was silence from God - He sent no prophet to them after Malachi until John the Baptist (Malachi 4:5; Matthew 11:13).

It is a mistake to equate long life and prosperity with God's favour, and evil-doers often seem to prosper (Psalm 73:3-12). However God will always reward His faithful ones (Isaiah 61:8): but He chooses His time and often waits a long time to bless us.  He chose the time for Jesus to be born (Galatians 4:4) even though it was 42 generations since His first promise to Abraham.  And He also knows the time when Jesus will return (Matthew 24:36).  So far, His time delay has been about the same as that from Abraham to Jesus (about 2000 years); and we do not know how much longer.  But we do know that He is coming and so we need to be ready to welcome Him when He comes again.  Is your lifestyle one which commends the gospel to others – particularly in how you honour your parents.  Is it obvious that you are living each day, in good family relationships, with the expectation that Jesus could come at any moment (Matthew 24:42)?