The entire program doesn't end on March 18 2005.

From the Apple FAQ on the program:

How long is the Expanded iBook Logic Board Repair Extension Program available?
The program covers affected iBooks for three years after the first retail sale of the unit or until March 18, 2005, whichever provides longer coverage for you. Apple will continue to evaluate the repair data and will provide further repair extensions as needed.

I bought mine in August of 2003 so I'm covered until August of 2006.

-zip

Also, the dates of manufacture listed here are incorrect.

Again from the FAQ:

Just noticed what appeared to be an illogical comment by me, but turns out to be a mistake by MO. It is May 2001 not May 2002 that the iBooks in question were manufactured.

Again from the FAQ:

The Expanded iBook Logic Board Repair Extension Program is a worldwide program covering repair or replacement of the logic board in iBook models manufactured between May 2001 and October 2003 that are experiencing specific component failures.

-zip