If you choose any payment option for memberships, your payment is automatically a recurring, ongoing payment. This means you never have to worry about signing up again. And it means also that if your membership had a win, you wouldn't have to worry about whether you missed out because you forgot to renew - you're always a member until you cancel.
If you don't want to have your membership renewed, cancel it before the recurring payment time. (See: How do I cancel recurring payments?)