Are you guys talking about the AMA's Introductory Program? If so, the following is copied directly from nationals website. The program lasts three months, not 30 days. Maybe I'm confused about what program your all talking about! Anyway:

AMA “Introductory Membership” Program

Thank you for your interest in our new Introductory Membership program!

Program Overview:
$19.95 cost for duration of program Membership valid for 3 months from date of acceptance, expires at end of 3rd full month, USA only. Fees are transferable to a full membership within the ninety day program (You must contact the AMA Membership department at 1-87-RENEWAMA (1-877-363-9262) before your trial membership expires).

Qualifications:
19 years old or greater by July 1st, 2006
First time members only, one Introductory Membership term per new customer

Program Benefits:
AMA insurance coverage, Model Aviation Magazine, Access to members only section of website, Ability to fly at thousands of AMA chartered club sites with appropriate club membership, 24/7 toll free verification – 1-800-I-Fly-AMA(435-9262) Ext 350