If it's 50 years old then yes it can live a very long life!
It seems unreal to me too, but I don't know either.
I guess as it's rhizomatous the chances are it will survive better than tuberous, although it would have to be well looked after.
I found one 38 years old, must be a toughie.
http://forums.gardenweb.com/fo...
It's been around a long time!
http://en.hortipedia.com/wiki/...