Actually, transformer cores do "wear out".

Care to elaborate?

These large capacity transformers typically last 10-30
years and fail for many reasons (other than overload).
Some of the issues:

* Ingress of air and water. This changes the dielectric
* properties of the core and can, of course, lead to
* corrosion problems.

* Problems related to the coolant (typically oil). The
* oil can break down, there can be ionization, production
* of gasses and more.

* Laminated cores can delaminate.

* Insulation can break down over time.

* The magnetic properties of the core change over time
* making the transformer less efficient leading to the
* production of more heat.

Often what starts out as a minor problem creates a hot
spot within the core. This deteriorates further leading
to a more catastrophic (and spectacular) failure of the
device.

--


well ok,,,

those certainly are failure mechanisms, but I wouldn't call them "wear
out" ,,, but that's just me...

Mark