This is all pretty interesting. I've been out (pretty much) since I married (an "Unbeliever"!!) in 1984. Since I was out there supposedly preaching about "this generation not passing away" in the 70's (and I remember someone from the stage saying the "age of understanding" was 13) I know this was not even questioned at the time. **To be clear, we were going out in the Field Service all through the 70's and early 80's telling people that Jesus became the king in heaven in 1914, there were all kinds of global "signs" to that effect and that the generation that "saw" those signs would not die before the Great Tribulation. "Seeing" the signs at that time meant old enough to know something cosmic was happening and that was defined as being "about 13". **
I've since asked my mother (still in) a couple of times about this because it seemed to me that anybody in their early teens in 1914 would be gone. First she told me that the "understanding" on this had changed so it could include anybody ALIVE in 1914-including newborns. More recently she told me that the "definition of generation" had been changed. Her explanation was a little vague-I could tell she was uncomfortable. Though she's a diehard, she's smart enough that this stuff makes her nervous. I didn't pursue the topic at the time, but thanks to all of you I think I understand the new definition. No wonder she was uncomfortable...