The number 40 in the Bible

There are a number of places where the number 40 appears in the Bible. The following are some examples:

The rains (in Noah's day) fell for 40 days and nights (Genesis 7:4). Israel ate Manna for 40 years (Exodus 16:35). Moses was with God in the mount, 40 days and nights (Exodus 24:18). Moses was again with God 40 days and 40 nights (Exodus 34:28). Moses led Israel from Egypt at age 80 (2 times 40), and after 40 years in the wilderness, died at 120 (3 times 40; Deuteronomy 34:7). God made Israel wander for 40 years (Numbers 14:33-34). 40 stripes was the maximum whipping penalty (Deuteronomy 25:3). God allowed the land to rest for 40 years (Judges 3:11). God again allowed the land to rest for 40 years (Judges 5:31). Israel did evil; God gave them to an enemy for 40 years (Judges 13:1). Saul reigned for 40 years (Acts 13:21). David reigned over Israel for 40 years (2 Samuel 5:4, 1 Kings 2:11). Solomon reigned same length as his father; 40 years (1 Kings 11:42). Elijah had one meal that gave him strength 40 days (1 Kings 19:8). Ezekiel bore the iniquity of the house of Judah for 40 days (Ezekiel 4:6). Jesus fasted 40 days and nights (Matthew 4:2). Jesus was tempted 40 days (Luke 4:2, Mark 1:13). Jesus remained on earth 40 days after resurrection (Acts 1:3). The Gospel Age Harvest was 40 years duration.

My questions for discussion are: What is the significance of the use of the number 40 in the Bible? What does it represent? What is it's importance? Why used so often? Your thoughts?

Bro. Harold