SEOs will tell you that you should optimize monthly on your site but I know that is not necessary. I was wondering what the real answer is or how often you do it.

I think it depends what industry you are in. If there are only a few websites devoted to your industry then probably not that often if however you have a realestate site monthly maybe the answer.

I think for 99% of the people you need to have the site initially optimized and then after that you need to work on getting links, writing unique content and developing a site that adds value to the user - that's what will drive traffic to your site.

We have our sites reviewed once per year

We had them optimized once and then we fine tune it as we go along