John from PA wrote in post #16172117
In reliability or failure analysis, a stated "life" is the point at which 90% of the components will still function. Stated differently, 10% will fail by the stated life. So, if Canon follows that statistical method of calculating life, at 100,000 clicks, 90% of shutters should still be working. The science of statistical analysis is quite advanced (re: Motorola and six sigma); in the case of a Canon shutter the numbers could also predict the percentage that might reach 1,000,000 and the number likely that would fail at 10,000.
It's an estimate of "average" shutter life, so roughly half should (theoretically) fail before that and half after. The figures are not arrived at by any scientific means and are clearly vague, as they quote 50k, 100k, 150k clicks, etc.
However, as with any technical product, a good proportion of the "before" failures are likely to be ones that let go quite early due to an inherent manufacturing fault, which shows up in the first 10,000 images or so. This is balanced by many bodies going way beyond the rated life.
Once you get past the initial risk period, your camera will likely give you long, reliable service and go past the rated shutter life. I don't worry about the figures though, I have never had a shutter fail and both my oldest bodies have passed the quoted rating (my first DSLR was over double its rated life when I passed it on to a friend, and it is still going strong in his hands).