Subscriptions can be recurring or non-recurring. Recurring subscriptions are automatically extended when they expire. When a recurring subscription is about to expire, an e-mail warning is sent. This gives the member the opportunity to cancel the subscription. However, when a non-recurring subscription is about to expire, I decided NOT to send a warning. Frankly, because I hate bothering people with e-mails. So, unless the member realizes that the subscription has expired, it may appear as though some of the forums mysteriously emptied. Of course that member can re-subscribe.

You can see your subscription expiration date by clicking Settings (at the top) and then Paid Subscriptions (down the list at the left). Not Subscriptions, which are thread subscriptions.