My understanding is that NXT liquid has changed since the initial release, but I don't know when exactly the change happened. If you got yours when it was first released, then what's currently on the shelves should be a different formula than what you have.
I believe the liquid was tweaked for VOC compliance . . . does anyone happen to know if Meg's made other changes as well? It does seem to me that people who bought NXT more recently are having much better luck with durability than I had with the original batch.