I've been on 400 mg for over two years and it's still working to keep the worst of the depression away. I'd been on 300 for a while before that and wound up in the hospital with the worst episode I ever had (I was actively suicidal). They took me up to 400 mg and it's done a great job. I don't know what I'll do if it ever poops out like the ADs I've been on did.