The shutter in a Nikon D4 camera is rated to go for 400,000 actuations. When the camera is new it is hard to believe I'd even hit the 400k mark, but with a shutter blazing away at 10fps it's easier to get there than you think. Recently, as with my D3 before it, I was coming very close to the end of the rated shutter life span. My D3 gave me indications that it was dying with intermittent malfunctions that never could be fixed by Nikon even after several visits to Nikon repair. In the end, I bit the bullet and replaced the shutter, and was glad I did.
Replacing a shutter sounds like a big deal -- read "expensive". Turns out it wasn't. At the time of my D3 repair the cost was in the $300 range -- not really bad when you consider this gives the camera a completely new life. This time around, as my D4 shutter began approaching the 400k mark, I decided to take some preventative medicine and replace the shutter before it began to go bad. Yes, it is possible the shutter would never have gone bad, but, recalling the shutter trouble I had had with my D3, I didn't want to take the chance of the D4 suddenly dying on me in the middle of a shoot due to an exhausted shutter. To spur my decision along, Nikon began offering a 25% discount on Nikon service repairs for NPS members, So off my camera went to Nikon to have the shutter replaced. It was returned a week later fully serviced in addition to the shutter replacement. Looks and feels just like a new camera. With the 25% discount it came to $336.
If I had tried to sell my D4 with that many actuations, I never would have received much for it. With that in mind, I consider the expense of the new shutter an investment in the value of the camera.