marking to see what you have to say. I've also reseached and still continue to as well on this topic. One thing that I noticed in the gospels is that Jesus was speaking of several different time periods but the way some are written it appears everything is jumbled together so people are mixing up what signs are what.
For example in Matt 24:1,2 when his disciples show him the temple Jesus says that "Truly I say to you, by no means will a stone be left here upon a stone and not be thrown down". Then in vs 4 they say, "Tell us, when will these things be" (WHEN WILL THE TEMPLE OF JERUSALEM BE DESTROYED!), then they also ask when will be the sign of his precense and the conclusion of the system of things.
So time period 1, the destruction of the temple, time period 2, his presence, and time period 3, the end.
Yet the WT and many others just read that and take the entire chapter to be talking about "the end".
When you read all the gospels you'll see distinctions between several of those time periods.
After learning all of that, it becomes very obvious that when he said, "this generation will by no means pass away...." he was speaking about the destruction of the temple and guess what, it DID occur to that generation. When reading all the gospels you'll see him straight out say that as for "the end" nobody knows and it wouldn't be during a time when anybody would expect it and it would be sometime after the 'era of gentiles'.