A long time ago, a man gave me a machine. I didn't appreciate the gift at the time, but the thing was an amazing piece of work. The system of interlocking pulleys, levers, and hinges is the best thing that I've ever been given.
The machine had an amazing system of resiliency and redundancy. If one component suffered trauma or began to fail under stress, the workload was shifted to other components. Where one piece was locked or weakened, another piece grew more mobile or stronger. The machine became even more powerful but with less degrees of freedom.
At present, the machine operates in these altered pathways, until one day those pathways also begin to suffer strain. Interlocking components will begin to fray or wear thin. The Machine will become stiff and slow. In time, gravity overwhelms the stacked segments. Those that angle front-ways will begin to fall forward and those that lean away will buckle backward.
The Machine will eventually accumulate rust, with gnashing together of materials that were not designed to withstand friction and compression. Now days, mechanics attempt to tweak and revise the patterns in which the machine operates. This can provide additional miles and hours of operation, but everything has it's limits. The machine may undergo a process of replacing dysfunctional segments. The new segments move better, but they never work as well as the original pieces. They too eventually wear down, lasting less than a fourth of the duration of the original components.
The Machines CPU usually declines at a slower rate than the mechanical pieces. In time, the machine will be less concerned with speed and strength or changing its environment and more with maintaining independent function. The machine usually falls into more of an advisory role.
It turns out that the CPU and the mechanical pieces rely on each other far more than previously thought. As one wanes, so goes the other. It's always sad to see or experience the decline and eventual cessation of function. But name any other machine with the capacity to last 70 to 100 years.
...for dust you are, and to dust you shall return.