Cancelled Membership and RSS Feeds

I've got a question regarding the Membership or Protected Content plugins.

I'm setting up a new podcast and we're going to make the podcasts available only to members.

The way I've done this before is to reveal the RSS feed only to people once they have signed up (via an email).

However this time I'm working on a monthly subscription and I'm wondering how I avoid someone signing up once, getting the secret RSS feed, and the unsubscribing. Once they have the RSS feed, how so I stop them from downloading the content?