Another problem with that mindset is that in a war, things won't be around for anywhere close to that long. What matters is how fast and cheaply you can build things, not how durable they are.
Nearly 300,000 planes built by the US during that war. Peak production in 1944 approached 100,000 new planes built in one year. The nature of the aircraft also changed substantially across the war, it's not like they took a few 1938 designs and churned out more and more each year. What was being made was constantly changing as their understanding of what was needed and what did or didn't work changed and engineering advances led to better systems (by some measure).
These weren't planes meant to last a century like the B-52 is currently targeting.
The JSF project began in 1993 (studies) with competitions later. First flight training batches delivered in 2012 and it reached operational status in 2015. 22 years from conception to operation. A grossly unsustainable approach for a military capability. It's not even one of the worst systems I'm aware of.
