Heh, that's funny, because I had always heard that of all the Guerlain scents, Heritage was the one that most people associated with "old people".
I personally don't understand this whole idea that some perfumes just smell too "old". I am a young woman, if I were to wear, I don't know, Shalimar, I don't think anybody would mistake me for an old lady. Besides, I don't think there's anything intrinsically wrong with being older, so maybe I'm just confused in general. I think it works the other way too. One of my mother's favorite perfumes is Blush (Marc Jacobs) which most people would probably say was created for a younger crowd. But my mother loves it and it smells really nice on her. That's just how I feel personally, of course.