I'm glad St Johns Wart is working for you. For me it gave me temporary relief followed by the deepest darkest Depression I ever experience. And repeatedly.
Since then, when my mood needs to be evened out, I reach for SAM-E. It works right away for me (with 400 mg) and I almost never have to take it two days in a row. Usually take it when I feel terrible and forget about it for months afterwards (unless times are REALLY tough).
So if the St Johns stops working for you, try the SAM-E. By the way, the Nature Made is the best brand I've found. And you can get it in grocery stores, drug stores, Costco, etc.