Just read a new post on another forum that I frequent about a person who sent his D600 to Nikon Canada because of the monthly "spotting" issue...lol...they replaced his shutter box! His camera was one of the first in Vancouver btw
If I owned a D600 I would be sending it in to get a new shutter box if I were you all. You spent a running ton of money and if they have fixed the problem you deserve to not have to clean your sensor every few hundred snaps I'm just saying...
Well I'm not sending mine in. I've cleaned the sensor maybe twice and I've got around 6,000 shots. I almost never shoot anywhere close to f22 and for normal situations, the dust does not show at all. And, if I'm right, the problem should disappear after usage. And, my camera is still under warranty and I'll take it further to see how it goes. If I feel I want to have it repaired, I'll wait closer to the end of warranty so I get an almost new camera after many many shots taken.