What is the life expectancy of a transformer? 20, 30, or 40+ years?

In the real world, transformers will be working at reduced average loads which could greatly increase the life expectancy of a transformer.

Old TYCO PRO REAL RACING 608R HO Toy Race Car Track Electric

Transformer Reliability Decreases with Age

How Transformers Age

Introduction To Transformer Loss Of Life - CHK Power Quality

Transformer Failure: Frequency and Causes

What is the Average Life Expectancy of a Transformer ?

30 KVA Transformer Primary 480 Secondary 208Y/120 Jefferson 413

Lionel Rio Grande 8213 only runs in reverse

power transformer