Our Note 3 is one of many that incorporate it. I've never seen one break but I guess if you were determined and parked a car on it or beat it with a hammer...
If you have at least a 25x magnifying glass, or an electron microscope - turn the screen off - but shine a dim light on the bottom right corner of the Note 3, or any of the above -
and you will see:
"Expiry 1 April 2015"
on any GG3 glass.
We will just have to be a little more careful from that date.