Here's how: 1  Stand with your feet shoulder-width apart and knees bent slightly. 2  Lean forward, placing your hands just above your knees. 3  Round your back so that your chest is closed and your shoulders are curved forward.  Then arch your back so that your chest opens and your shoulders roll 1  back. Repeat several times.
Typically this count is between 100,000 and 300,000 shutter actuations, with the latter limit associated with the EOS-1D models. In fact, the Camera Shutter Life Expectancy Database is a really neat user-based site for DSLR models of several brands, including Canon.
A slow shutter speed lets in more light. The shutter is open longer. The shutter speed us usually shown as the reciprocal of the time that the shutter is open. A shutter setting of 60 represents 1/60th of a second. A shutter speed of 1000 represents 1/1000th of a second.