It's like a motor to a car.
In general, a car is considered to be old, or becoming old at 100,000 miles.
I disagree, if well maintained, I think that's just being warmed up and can easily run 300,000.
That number about the shutter actuation life, is an expected life span, not a guarantee.
It's expected to last that long, but there is no spec sheet showing the true life span, they don't know.
I think if the camera wasn't abused, I think the shutter will last a bit longer.
But even thing's like climate, smoke-free, non smoke-free and stuff can change that.