You may be right - I have just not had this problem before. I don't know how the sharpness could change over time.
Here is shot taken recently, one that I would have expected my D3 and 70-200 to nail with VR turned on. The fact that nearly nothing is in focus might suggest my hands are getting shaky or that VR was turned off. That it is happening so regularly makes me wonder if my focus is off. I didn't become a crappy photographer over night!