What is the lifespan of a level D simulator? We have a few interesting questions about the normal ways aircraft end their lives.  What about simulators?  How long do they typically last?  What is the typical reason for retirement?
I am particularly asking about high level simulators used for airliner type ratings.
This question was inspired by discussion of the time taken to reboot a simulator:
Do Flight Simulation Instructors stop the simulator before a simulated crash?
Related questions:

Why are some aircraft&#39;s life limited by both cycles and flight hours?
Under what conditions do airliners retire aircraft and sell them to other airlines?
What limits the lifespan of helicopters?
What is the lifespan of commercial airframes (in general)?
As long as it's maintained, and replacement parts are available, there is no limit. Although maintenance could end up costing more than the simulator itself:

CAE says the Series 5000 will offer a 25% reduction in lifecycle costs, which tend to be two to three times the original cost of the simulator during a 20-year lifetime (...)
— flightglobal.com, 2008

The 20-year lifetime mentioned above is what would a training center expect, as that's typically how long an airliner model stays in service in sufficient numbers to promise a continued demand.
Delta Flight Museum still operates a full-motion 737-200 simulator (Delta introduced that model in 1983, almost 40 years ago).