I always encourage people to make their claims on any possible problem before the warranty expires. However, I would recommend trying to register the unit on the website, and then call back 800-SAMSUNG to see if they'll honor the extension (U.S. only).
You can register it here:
My LN-T4665F TFT-LCD TV just clicks and won't come on anymore. Been doing it since before the warrantee expired but now don't come on just clicked. Tried to contact samsung but they say I didn't register it. I can't figure this out since I know I did because I did a powered sub woffer from a differant company the at the same time and still get e-mails from them.