Well Stephen, what about Genesis 5? Why is that chapter in our Bibles? Why do I need know that Adam lived 930 years and died? Why do I need to know that Seth lived 912 years and died? Why do I need to know that Enosh lived 905 years and died? Why do we care how old these people were when they died? Here a couple possibilities. Perhaps God wanted us to be able to use those numbers to do some calculating regarding when the flood came. Perhaps He wanted to show us how strong and full of longevity those initial, physically-pristine human beings were, outliving most of us today by ten times or more. Whatever the case, I believe God included the numbers for a reason.
Additionally, it could be that the Holy Spirit saw fit to inspire Moses to compose this section of text for the purpose of repeatedly reminding man that he will die physically. Although there are two notable exceptions in Enoch and Elijah, everyone else who has ever lived has succumbed to physical death. Genesis 5 records the same phrase over and over again - "...and he died." The phrase is used eight times to be specific. It should be noted that physical death was not the end of any of these men of old; their spirits live on today. However, the point is that physical death is essentially unavoidable. Even if you live to be one thousand years old, as Methuselah almost did, you will still die. It is not so much a matter of "if," but "when."
A surface glance into Genesis 5 will reveal a wealth of chronological and genealogical information, though most of it is not very practical for our purposes today. But, a continual reminder that physical death is ever approaching is practical and worthwhile for any mortal. The purpose of such a reminder is not to cause depression or a sense of futility--just the opposite. When we realize and remember that each day we are one day closer to death, and one day closer to the Lord's return, we should be compelled to live righteously, using the precious moments we have in service to God--whether we be given 20 years or 120. Remembering that there is more to our existence than this physical sphere of disappointment, disease, and death, should bring much joy, not sorrow, to our lives. Physical death should not be feared but rather prepared for, both mentally and spiritually. Friends, have you come to terms with your own mortality?