I've read one of Alfred Dunhill's books called The Pipe Book, and it also suggests that tobacco might've been native to Africa as well due to the nature of historical finds of pipes and such from tribes in Africa to tribes in South America.
I can't say how long it lasts other than what I have experienced. When I first started smoking my grandpa and I open open a tin of tobacco that he'd been saving for 20 years, I don't remember what it was, but it smoked fine for my tastes. I also just open a bag of aromatic tobacco that I got when I first started smoking about ten years and it was fine, a little weak, but nothing major.