There are a lot of variables that make it very difficult to give you any sort of definitive answer. The root of it all though is that the appraiser is an independent business person who is hired by the bank, not NACA. That makes it three degrees of separation between you and the appraiser, with an element that is beyond your control or ours.
Also, the dispute usually means the appraiser is going to pay another visit to the property, which has to be fit into his or her schedule. That in turn can cause a delay, depending upon how tightly they are booked.
I’m not terribly surprised by ggof3’s comment that hers took two weeks. That’s longer than anyone wants to see, and most have shorter turnaround times, but it’s an unfortunate reality. Hopefully yours will be shorter.