In my experience, therapy is helpful, as long as you a) have a good therapist and b) commit yourself to it.

As far as how often to see your therapist... ideally, I would see my therapist every two weeks normally, and once a week when in depressive episodes. However, I see my therapist at a clinic, so I'm lucky if it's even every other week. It's usually three or even four weeks between appointments. Do I wish I saw her more often? Yes. But having sporadic therapy sessions is still, for me, way better than no therapy at all.