is the "paid subscription id" for users persistent?

[dethier]

I'm creating an automatic upgrade script for my commercial plugins that I want to integrate with s2member and I'm considering using the "paid subscription id" as an api-key of sorts to verify that a user has access to the plugin when their client install tries to access it.

However, I need to know if this "paid subscription id" is persistent with a user if their subscription period elapses and s2member downgrades them to a lower capability. When this occurs is the id deleted or does it stay?

In another scenario, and related to this; if/when a user renews their subscription doe the paid subscription id stay the same or is it changed?