Hi Scoot,
Your correct, it was a warning unto when God would destroy the Earth by flood. There is another writing that even discussed this called the Book of Jasher where Noah gives that warning to the people. However, with everything in the Old Testament, everything is a type of something else.
God's Spirit continues to STRIVE with man even unto this day, showing that the meaning was beyond the type. There was found the Book of Jubilees among the Dead Sea Scrolls, where the scribes were counting the years according to these Jubilees. I believe they knew that there would only be 120 of them.
Additionally, we need only follow the type. Moses was in the wilderness for 40 years, for 40 days and nights was Noah subject to the rains, Jonah would warn Ninevah for 40 days, Jesus was tried for 40 days and nights in the wilderness, Jesus remained with the Disciples for 40 days after His Resurrection. The leaders of Israel would rule for 40 years. A generation is for the most part 40 years. Remember the generation that rebelled against God would be destroyed and not go into the promised land and that took 40 years. So we have evidence that a generation would be 40 years. Jesus said that generation would not pass until all these things be fulfilled. I believe HE was referring to the Generation of 40 Jubilees years in which the Church (Congregation) was being purged just like the type (Congregation of Israel) was purged in the Wilderness under Moses.
So Scoot, you learned something very good in understanding the type. After all we must know the type before we can know the fulfillment of the type. Now a Jubilee length is discussed in Leviticus 25. I would urge all to go and read about it.
