I stopped taking it as I didn't feel the need to. As far as I can tell there's no reports on long term usage.

As for side effects, was a little harder to sleep, and I had to remember to eat. I lost about a stone in a month, but then my appetite came back.

Oh, and it has asparagus-like effects on the body.

I've still got some in a drawer I keep for the days I've got a hangover. Beats the hell out of coffee & a fry-up as a cure.