Alright, time to clear up some stuff.
AppleCare covers you for 1 year from date of purchase, with 90 days of phone support. This is standard. The AppleCare you buy bumps each one of those up to 3 years.
1-800-SOS-APPL is AppleCare's phone number. You should be able to find that in your stack of manuals.. the one that says AppleCare on it... that you mail in/fax in.... etc.
If Apple claims you get 18 hours of battery life, then you must be able to get 18 hours of battery life! Look at what is happening with the 3G iPods. Apple said 8 hours, and there was no way in hell people got 8 hours. Now, if you had no backlight and didn't skip tracks and got 8 hours, it would be different. But that didn't happen.
If you aren't getting 18 hours of battery life, call Apple. They will probably be able to help you. And then you can drive to an Apple Store and they may be able to swap batteries there, or you can send it in to Apple and they will send you a fixed/new one.