I was surprised to learn today that canceling my amazon prime membership won't give me any refund (not even a single dollar) if I have placed any (or just one) order using my prime membership benefit. My previous understanding was it would be a proactive refund. Amazon!
Here is the link to the Amazon Prime Terms & Conditions (under the Membership Cancellation section).
Now, I will have to keep ordering more every single day to make the full use of my membership