I was in a massive depression when I started it in 2008. By three weeks' time, I was markedly improved. It got better from there. Lithium is traditionally considered to be better for mania, which is why it is so often paired with Lamictal. Lamictal did zero for me. Lithium probably saved my life, at least that's how I feel today. There is no question it has had a big impact on my depression.
You may have some dry mouth between the lithium and the Wellbutrin, but mine's not terribly bad.