Why does God take so long to fulfill His promises?

All things are possible with God.
—Matthew 19:26
When God came to Abraham and told him that He was going to bless him, Abraham said to God, "That's fine, but what I really want is a son." God said, "I am going to give you what you ask for," but He didn't give it to Abraham right away. The Word says, Abraham was a hundred years old when Isaac was born (Genesis 21:5). Actually, twenty years went by from the time God promised Abraham that he would have a child to the time that child was born. In fact, Abraham was already old when God first gave him the promise of a son.
By the time Abraham fathered that child, his wife had already gone through the change of life. She had a barren womb. So Abraham and Sarah not only had a prayer request, they also needed a miracle.
Isn't it interesting that sometimes when you ask God for something, He lets it go so long, the only thing that can possibly produce what you asked for is a miracle? Why does God do that? Because He likes to show Himself strong in behalf of those whose hearts are blameless toward Him (2 Chronicles 16:9).
When Martha and Mary sent for Jesus to come and minister to their brother, Lazarus, who was gravely ill, why did Jesus wait two days longer, until Lazarus had actually died and was buried, before He went and raised Lazarus from the dead? It was because Jesus already knew what He was going to do for Lazarus.
If something is dead—a dream, a desire, a want, a need—it doesn't matter to God how dead it is. God can still bring it back to life in His timing because our God is an awesome God. Nothing is too hard for Him. That is why He is never in a hurry and why it seems as if He often waits until nothing will work but a miracle.