You can view all your previous payments and how they were used by clicking on the Account Balance menu in the top right-hand corner of the interface.
All services are tabulated by default by expiry date. This makes it easy to see when your services expire, or to extend them at any time during the year.
Importantly, each extension will add +1 year to the turn date, so you won't lose any of your subscription time even if you decide to extend sooner.