I was told by my pharmacist it was addictive - I was really surprised, but it did explain why I needed more and more just to get to sleep - and stay asleep! Like KJ, just in a few days my tolerance was up and I needed it.
I still use it from time to time, when I've worked myself up into a state about not sleeping - but never for more than 3 days. I find that is a good limit for me.