I sure HOPE they don't degrade with age. I'm already old and feel sometimes like I am degrading! But I have not experienced this with eityher of my D700 bodies. I have not experienced what you describe -- and I hope it isn't contagious! I would try test shots to try to recreate the phenomena and then examine possible causes. If you have indeed changed something about how you work or how your camera is set up, you may be able to disgnose the problem. If not, you might start by going to a good professional camera store and finally, a camera repair facility (Nikon authorized)if you still can't overcome the issue. Good luck!