Should flywheels on stationary trainers be replaced periodically to avoid catastrophic failures caused by fatigue? I have owned a Computrainer stationary trainer for 20 years and recently had the flywheel shatter, sending shrapnel through the walls and ceiling of my basement, as well as into my hamstring.  Should flywheels on stationary trainers be replaced on a regular basis to avoid fatigue-induced failures?  How often should a flywheel be replaced?
Apparently you are not the first victim of this problem:  http://www.saferproducts.gov/ViewIncident/1237585

I suggest you should also submit an incident report to the CPSC (assuming you are in the US).  Since you were injured you may also want to talk to a personal injury lawyer.  RacerMate's website claims they offer an "indestructable build".

The manufacturer should provide guidance on the safe use and maintenance of their products.  I'm sure they are aware of this type of failure.

Update:  the currently shipping Computrainer flywheel is apparently made of copper.  That sounds like it would be less prone to shatter.