I did a Jeff Walker style internal launch to my list for a new product and then I set up the entire funnel as a perpetual launch. Visitor opts in at landing page and is sent to the first launch content page in the 11 day long launch sequence.
Besides warning of the impending end of the launch in your emails, what are you doing to create a sense of urgency? How are you "closing" the launch? Are you using a countdown timer that redirects to a "launch closed" page at the end?