This is pretty long but if you are interested in subscriptions / recurring and are a drupal developer its worth a read and more importantly a comment / feedback please.
A while ago I needed to create a subscription based website. The user would be subscribing monthly/yearly for access to premium content, but we were not going to save cards on file and we didn't want it to be automated billing. We wanted notification emails to be sent out prior to the subscription ending telling them to buy a new one. When they did, their subscription time would be extended.