As far as I recall Watchtower's New Light doctrine was conceived from the very first issue of Zion's Watchtower and Herald of Christ's Presence, 1879. C.T. Russell used it then as an alibi for his failed 1874 and 1878 dates. 1874 was eventually replaced by 1914 and the rest is history.
Well, they've been using the alibi ever since -- for the some 24 failed events that were supposed to happen in 1914 to the 49 failed dates over the years.
At the heart and soul of Watchtower's "New Light" teaching is Proverbs 4:18, ". . . the path of the righteous is like the bright morning light that grows brighter and brighter until full daylight."
Few actually give thought about the person who actually penned those words.
Few think about the behavior of its author and how he completely ignored and grossly violated one of the ten commandments, "you shall not commit adultery". Yes, they had indeed been in effect for some 500 years before his day.
Few admit that he had more spouses than Hollywood celebrities Mickey Rooney, Liz Taylor, Larry King, and Zsa Zsa Gabor -- all combined.
Few mull over the fact that, by his orders, no less than 3 men were put to death.
Even fewer think about how so-called Watchtower's New Light teaching simply does not undo flip-flop doctrinal contradictions which are like a strobe -- flickering some 10 times for certain teachings. Think resurrection of the ancient Sodomites, the Superior Authorities of Romans 13, the transplanting of human body parts, the identiy of the Al´pha and the O·me´ga, the 1,250 prophetic days -- and others.
Most, however, are able to identify exactly who he is by his popular defining quality -- wisdom. ". . . Sol'o·mon’s wisdom surpassed the wisdom of all the people of the East and all the wisdom of Egypt. He was wiser than any other man, . . ." (1 Kings 4:30, 31)
Whether or not we have a timeline for Solomon's activities, we simply don't know when he was wise and wrote all those "inspired words" vs. when he had the 1,000 wives / concubines and when he had those men put to death. That said, it is reasonable to conclude that he was certainly not as wise as some think. It's also an unwise conclusion that "the bright morning light that grows brighter and brighter until full daylight" has even the slightest bearing in our day on whether Watchtower teachings evolve in one way or the other.
To most, "New Light" has morphed into "Old Alibi".