Yes, me too. I've had them grow for about 3 years in my front garden where it's sunny - I always leave a few dead flowers on & by the time they give up they've seeded in other places.
Believe it or not, I've got one too, it grows out of a crack in my crazzy paving every year and I dont have the heart to pull it out.
I think it's one of those bedding plants we treat as a "half hardy annual" but really it's probably a perenial from where it originates.
I thing I like about these is, when they have finnished flowering. you can nip the tops off and they flower again.