Premium Account is a monthly or yearly service.
The first monthly fee will be billed on the date the subscription process is completed, and will be billed on the same date each month thereafter. The next billing date will be the same day each month.
You can view your next billing date at any time on the Subscription page, which can be found by clicking on your account name in the upper right corner of the page. Click on your account name at the top right corner of the page to view your next billing date.