parshat Bereishit: Are The Antediluvian Ages Symbolic?

I've been discussing the ages in the genealogies in Bereishit 5 over the past few days (in a different context) with littlefoxling, and one thing I thought to consider is whether the ages given are intended to be symbolic.

Hirhurim did a bit on this, in another context about parallel genealogies between Shet and Kayin, noting, for example, that

Cain was told that he would suffer seven-fold vengeance (4:15). Kenan, in contrast, had Mehalalel when he was seventy years old and lived to the age of eight hundred forty (7 x 120; 5:12-13). It seems that Kenan very pointedly lacked Cain's seven-fold punishment.

and

In the fifth and sixth generations, the Cainite Mehujael and Methushael represent the destruction of their lines while the Cainite Enoch was taken up by God (Gen. 5:24) and Methuselah had the longest life.

I would note three other points. Other significant lifespans might not be immediately apparent to me, but might yield to further investigation.

The first significant lifespan is that of Adam. Here I am merely echoing the midrash that Adam was supposed to live 1000 years, but was shown by Hashem that David would die while being born, and so he gave 70 of his years to David. Indeed, 930 as Adam's age might well be significant in this way, even if we choose to part ways from this midrash. As we read in Tehillim, the days of man are 70 years, and for the mighty, 80 years. If we take 1000 to be the ideal human lifetime at this time period, and 70 to be the typical lifespan in the Biblical period, then Adam's losing 70 years might be cast e.g. as a fulfillment of God's promise of death to those who ate from the Etz haDaat.

Chanoch lived a short period of time, and walked with God, before God took him away. Much extra-biblical material has been written about Chanoch, including midrashic material. Bereishit Rabbati has him turn his body of flesh into one of flame and become a little YKVK with his own Kisei HaKavod, etc. Is it significant that this short-lived person lived a total of 365 years, the same number of days in a solar year?

Metushelach lived a total of 969 years, the longest of anyone in the list. Why? One midrash says that the flood waited for Metushelach to be buried, and indeed, if one does the calculation, he lived all the way up to the flood. This could be stating that he was an ideal human, who would have lived 1000 years if not for the flood, or that Metushelach, Noach's grandfather, was not welcome on the ark, and so died in the flood.

No insights into the other ages at the moment.