All U.S. nuclear weapons in the current stockpile were designed and produced in the 1970s and 1980s, with an original design life of 20 years. Since the end of U.S. nuclear production in 1991, the United States has developed and executed LEPs for weapon-types in the legacy Cold War stockpile.
https://www.acq.osd.mil/ncbdp/nm/NMHB2020rev/chapters/chapter4.html#:~:text=All%20U.S.%20nuclear%20weapons%20in,design%20life%20of%2020%20years.
美國的核蛋頭都過期了,靠LEP(life extension program)吊命?