The “metaphorical” meaning (or at least the symbolism) as it was presented when I was a student was that long life was a blessing from God. God bestowed long life as a reward on those who behaved in a manner He favored. Note that (with only a couple of bumps) there is a steady dimishment of life throughout. This was taken to mean that people were behaving more and more evilly and that even God’s chosen patriarchs were gradually becoming more sinful. Specific years were not important and there could be “better” men (such as Enoch) among the increasingly sinful lineage, but the general progression was away from God until humanity finally hit a point where their relative ages stabilized along with their sinfulness.
Most Bible scholars I’ve read say that God was saying that in 120 years, the flood was going to hit, not that mankind’s lifespan was going to be limited.
Well in my last post, in my reply to UDS I said how I thought it was strange that Noah, who was a “righteous man, blameless among the people of his time, [who] walked with God” didn’t live as long as Jared and Methuselah. But now that I think about it, Noah did get drunk and naked…
It seems unfair that Adam, who disobeyed God’s big law about eating some fruit (though he also spent a day naming animals and fathered many children) got to live 930 years, but Moses only lived for 120 years… Abraham who was willing to sacrifice his own son to God only lived for 175 years…
BTW, remember that in Noah’s time, people were so evil that God decided to kill them all! And yet those who lived in Noah’s lifetime (his father and grandfather, etc) lived to 777-900+ years… Since Jesus’s disciples presumably didn’t live very long that implies that the disciples and those in Jesus’s time were far more sinful than those in Noah’s time…
There are some verses in Proverbs though that say if you obey God’s laws (one of them happens to be to love the Lord with all your heart, mind, soul, and strength) you’ll live longer:
Proverbs 10:27, 19:16, 19:23, 21:21.
Though Ecclesiastes 7:15 says:
“My life has been useless, but in it I have seen everything. Some good people may die while others live on, even though they are evil.”
Perhaps that is the exception to the rule.
So even if people live longer (metaphorically or literally) because they are less sinful, I don’t understand about the age at fatherhood.
Name / lifespan / age at fatherhood / %
Adam 930 years 130 years 14%
Seth 912 years 105 years 12%
Enosh 905 years 90 years 10%
Kenan 910 years 70 years 8%
Mahalalel 895 years 65 years 7%
Jared 962 years 162 years 17%
Enoch 365 years 65 years 18%
Methuselah 969 years 187 years 19%
Lamech 777 years 182 years 23%
Noah 950 years 500 years 52%
(for the percentage I just divided age at fatherhood by the lifespan)
I would have thought it would be more common for men to father children later in life… well I guess women would stop being fertile at a rather young age and Noah remarried or married very late…
The “age at fatherhood” ages don’t seem to be very meaningful… e.g. Noah had the highest one (500) even though his age at death is the third highest, and Lamech had the third highest (boy at the age of 182), even though he only lived to 777, where the next lowest age is 895… Mahalalel, who lived to be 895, fathered a son at the age of 65, which could easily have happened. 
Thanks for the info. The commentaries I’ve looked at now say the same thing…