I've felt very little change in my Sadowsky neck finish feel over time (about 4 years now on one, and about a year on the other). Again, I love the profile of the neck, the stiffness, etc., etc. It's just not my favorite finish compared to a nice satin poly finish or other Nitro finished necks I've owned and played.
That being said, I actually really like the neck finish on my 2005 Alder/RW NYC (the one that is for sale on the Sadowsky site at the moment). It is quite different from the finish on my newer NYC, and is closer to the Alleva and old Fender finish. I've played Sadowsky's with each of these types of Nitro finish (i.e., the finish that is relatively shiny and smooth right at the start, and the finish that is more satin and 'sticky' at the start), so there seems to be some variability in the batches of Nitro (which Roger I believe verified in one of these threads). Also, my current Sadowsky has a vintage tint, whereas the one I have for sale does not. I'm not sure if that tint somehow interacts with the Nitro resulting in the different feel, but they are WAY different.