This has been working extremely well for me, Amy.
My only "complaint" is that the first time I ran it, I had (obviously) an extremely large group of people e-mailed. Now, every day I run it, I only have 8-10. But when it hits the 31st day since the first time I ran it, it's going to grab that huge list again, minus the people who actually came back.
Since I don't use the delete option...If you use it, you don't have that problem
It's too bad I didn't plan ahead, and slowly decrease the number of "inactive days" when I first ran it.