shutter count is a counter that counts how many times the shutter has been pressed since it left the factory, Depends on the model, the expected life of the shutter mechanism is around 100,000 to 150,000. But that does not means after 100,000 actuation, the shutter will fail. It is just an estimate similar to the hard disk MTBF (mean time between failure). When the shutter mechanism fails, you will need to get it replace from the service centre.