You know the "Do Not Call" list has expired when...

you get a call which consists of a recorded voice informing you that the "warranty" on your "vehicle" is about to expire, and you don't own a car or even have a driver's license.

Edited to add:
Online research indicates that registration has not, really, expired.

The Federal Trade Commission will not drop any telephone numbers from the National Do Not Call Registry based on a five-year expiration period pending final Congressional or agency action on whether to make registration permanent.