What about metal fatigue?
Bombers aren't like other planes. They're built to endure proximity blasts from flak or SAMs, and soak up punishment from cannon fire and keep fighting.
They're flying tanks, which is why the first generation of hurricane reconnaisance planes were just bombers fitted with instruments.
A B-52 once landed without its vertical stabilizer. Maybe it sheared off from metal fatigue, but it flew for five hours after losing it and landed safely regardless.
"As a result of the incident, the B-52H airframe was strengthened to deal with future gust load turbulence. The bomber involved in the incident, tail number 61-0023, was repaired and returned to service, where it served for another 44 years on active duty. On July 24, 2008 it was the the first B-52H to go into storage at the "Boneyard" at Davis-Monathan Air Force Base"