Now I'm confused. Within 5 years of what? The NG certainly didn't go through a full certification procedure, did it? In the same way that a -600 didn't have a certification distinct from a -800 (or an A318 from an A320 even though they are the best part of 15 years apart).
What you're explaining is that the NG must have had a full certification done on it because it was more than 5 years from the certification of a previous model of 737? So it had a full evac. test, and all of the structure was therefore fatigue tested? Fuselage and wing included?
It boils down to this - was the wing fatigue tested or not? If yes, super. If not, why not, as it is a "new" wing?! (thanks for your patience - sorry about thread creep...)