I am the developer of the PayPal Buttons module. PayPal subscriptions (also known as recurring payments) are handled by PayPal, so the seller does not need to resubmit the payment. Instead, PayPal charges the customer based on the payment schedule defined by the store (and accepted by the customer).

The PayPal Buttons module integrates with the Subscriptions module that I also authored. The Subscriptions module invokes Workflow-ng events when a subscription is first registered, when it is renewed, when it reaches a configurable notification threshold, and when it expires or is cancelled. This can be coupled with Workflow-ng actions, such as role modification, to create subscriptions that grant access to site features while active.