In the process of selling my Nikon D90, I was asked by an interested party how many clicks there were on the camera. That’s another way of saying how much life is there left on your camera shutter. I do not know what happens when one reaches the point where they have 100% of the clicks, but manufacturers rate various cameras for shutter life. That might also be a good idea to know prior to buying a camera.
On my d90, I learned that I had 35,235 clicks on it, or had released the shutter that many times.. The process is simple. Just take a picture of anything. The site will prompt you to do a browse for that image, then ask you to upload it. Once uploaded it reads the image to produce the number of clicks it has on it.
Here is the program http://www.sno.phy.queensu.ca/~phil/exifto