Your membership will automatically renew until you cancel it. If you buy a yearly membership. It will instantly renew it until you decide to cancel it. So no, you don't have to renew it manually every time it runs out.
I ran into the same question when I was considering buying two bundles at once. I'm still at a dilemma with this. If I buy two bundles and select the one-month-membership option on both, will I get two months in a row or am I wasting money?