Yes, all subscriptions automatically renew themselves whether it is the monthly, quarterly, or yearly. However, you are able to cancel and/or modify your subscription at any time by logging in to your account and going to Settings > Your Subscription > Edit Subscription > Cancel Subscription. If there is any time remaining on your subscription when you decide to cancel, you will still have all the features of an upgraded account for the remaining time you paid for.
For example: If you sign up on January 4 your next billing date will be February 4. If you decide to cancel before this renewal date, your card will not be charged again and you will have access to an upgraded account until February 4.