Why the B-52 is outliving newer bombers [video]
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1. Over engineered
2. More generic design choices (easy to upgrade)
3. Continued support to upgrade it and keep it relevant
4. "the crew concept" (not really sure how this supports the title claim)
In general it's almost always cheaper and less risky to reuse something than to start from scratch and design/build something new. The downside is the longer between clean sheet designs, the more knowledge is lost on how to design something from scratch.
>These aircraft were designed with slide rules plus 20 percent for structure components.
50 years is a long time for a piece of machinery. There will be many failure modes that will be discovered in these planes.
The C-130 was thought to last forever. Until about 10 years ago, well used planes being used for firefighting starting having structural failure in flight. Suddenly, organizations flying the older airframes decided that it was no longer effective to take the risk of failure.
The old heavy tankers were all being flown at their limits for decades with nothing more than a dude with a flashlight looking at the insides of them and going "yurp, this is good to go!"
On Air Force aircraft, to include the B-52, thousands of inspectors either look at every single critical part on a regular basis or use random sampling to establish estimated fleet health levels.
https://www.airforce.com/careers/maintenance-and-repair/nond...
I'm willing to bet that each individual B-52 has more paperwork on it and more eyeballs that have seen x-rays and ultrasounds of it than every single aerial firefighting platform in the world combined.
Firefighting is uniquely hard on airframes. It imposes all sorts of loads on aircraft that they just don't experience in "normal" operation. For maintenance purposes, one well-known (V)LAT operator I'm familiar with treats one hour of firefighting ops as 7 hours of flight time.