Currently, quotas for stock images are issued on a monthly basis, and you can see the number of available images remaining each month from My Account → Subscription → Remaining quota for paid image usage.
Your quota is updated monthly as long as you are a continuous annual or monthly subscriber.
For annual subscription users, you may see that the expiry date of the subscription plan does not match the expiry date of the paid images. This is because the image quotas are issued on a monthly basis, so the expiry date here only indicates when the most recent month of expiration. It will automatically renew on the next month.