Not sure if this is entirely relevant to your question. But it is a fascinating study close up. Thanks for bringing it up. I did have to refine my view somewhat.
Thus it may not be specifically relevant to what you're asking, but the chronological application of 120 years in relation to a "generation" of Noah's day is applied from 1874-1994. This parallels a "last generation" of 80 years from 1914-1994. The context of Matthew 24 is clearly about the second coming events vs Armageddon. Remember, Jesus Christ first arrives when Satan is kicked out of heaven and he is in the earth loose for a short while during the time Jesus Christ seals the elect. This is done by the angels and thus secretly and invisibly. Thus the illustration of two in the field or two in the mill house, where one is taken and one is left behind.
Matthew 24v 36 “Concerning that day and hour nobody knows, neither the angels of the heavens nor the Son, but only the Father. 37 For just as the days of Noah were, so the presence of the Son of man will be. 38 For as they were in those days before the flood, eating and drinking, men marrying and women being given in marriage, until the day that Noah entered into the ark; 39 and they took no note until the flood came and swept them all away, so the presence of the Son of man will be. 40 Then two men will be in the field: one will be taken along and the other be abandoned; 41 two women will be grinding at the hand mill: one will be taken along and the other be abandoned. 42 Keep on the watch, therefore, because YOU do not know on what day YOUR Lord is coming."
There are two specifics here. The PAROUSIA (presence) of the messiah, and his COMING or actual arrival. If we apply both separately to the 120 years, his coming would have to occur before the 120 years were up, and the activities of his "parousia", that is, those specific things in preparation of the coming would occur during the 120 years. Thus it could be interpreted that Christ's "presence" would occur over a period of 120 years. So even though the Bible students were expecting Christ's "arrival" in 1874, which didn't happen, that is only partially true, because his "presence" could be said to have begun in 1874, in which case you have a chronological parallel specific to 120 years in relation to Noah's generation.
But there are so many potential interpretations, obviously. So I just wanted to note that some of the elect, like myself, consider the "generation" of Noah's day of 120 years to be fulfilled from the beginning of Christ's "presence" in 1874 until 1994, the generation that ended after the Christ's arrival in 1992 (based on the fall of Jerusalem in 529 BCE vs 607 or 587 BCE).
LS