The “camera shutter sound†is known throughout the world; even some birds know it! The technical term for that sound is called “shutter actuationâ€, which is the process of the camera’s shutter completing a single cycle.  Like all mechanical parts, the shutter will eventually wear out no matter how well you take care of your camera.  Read on to find out how you can get more life out of your DSLR camera as it relates to the modern focal plane shutter.
So, what causes the shutter to fail?
Shutters can fail for many reasons. Shutters have two sets of very thin blades that open and close at an extremely high speed and travel along a very tight pathway. If those blades are disturbed in any way, the camera will cease to function normally. Normal wear eventually ends with mechanical failure. Mechanical defects typically show themselves fairly quickly. Physical obstructions can cause the shutter to fail (and damage other components along the way); it only takes something little falling inside the mirror box and wandering into the shutters travel path. The shutters flash synchronization switches can also become damaged from extended or over use that causes heat or wear, which ends in an error and a failure to actuate. Power supply issues, like faulty grounding or damaged circuitry, can also result in shutter failures. These can be slow to manifest as problems, due to the power fluctuation tolerance, but will degrade eventually.
How long should I expect my shutters lifespan to be barring no defects or physical damage?
They can last up to 300,000 actuations; however, the answer to that question is dependent on what camera you own. You will need to refer to the manufacturers estimated shutter life expectancy for your particular model. For those models that do not have any published shutter life expectancy estimates, you might try Googling around a bit but take any information you find with a grain of salt.
How can I tell how many actuations are on my shutter?
Modern digital SLR diagnostic software that repair facilities use can provide an accurate shot count; this is something you will most likely have to make a special request for from your service provider when you submit your camera(s). Sometimes, cameras will embed this information in the image’s ExIF data. There are a number of ExIF data reading softwares out there to view this information. Unfortunately, they aren’t endorsed or approved by the manufacturers, so this method can’t be fully recommended.
When should I have my shutter serviced?
A shutter doesn’t always fail catastrophically; it may malfunction intermittently or so subtly that you may not notice.  The shutter will typically fail completely after a certain length of time however. The software that repair facilities use can also identify error codes and run a series of tests to determine if a shutter has an issue. If you are using your camera on a regular basis, it is recommended to have it checked at least once a year. If you count on your camera for your livelihood you will want to have the shutter replaced before it reaches the threshold of the estimated life expectancy to prevent it from failing when you need it.