You do not have to worry about renewing your domains.
We will send an email with billing information for renewing your domain. If you miss it, we will remind you this couple of times, when we don´t receive a payment.
Always at our Customer Center, you can find an overview of your managed domains with us. You will see here also the expiration date and on the main page, you will find if you have any unpaid services like on the screenshot below.
If you are not interested in the domain, just contact us and we will release it for someone else or you can ignore the invoice and domain will be deleted automatically.