Maybe that's the cause of the delay. They had to figure out how to 'refresh?' them.
That USED to be true with the old Polonium [?] based "Initiators" in the Nagasaki and Trinity devices.
It has been a long time since I studied Nuclear Engineering [our college had three research Reactors, including a CRITICAL, Heavy Water moderated one].
Some years ago, the ESONOMIST had a review of the way modern Nukes are initiated, and if I remember correctly, a Vaccuum Tube is fired up to supply the stream of Neutrons to accompany the Implosion.
I have no clue as to just what the Physics of a Vaccuum Tube supplied Neutron initiator involves, but it would seem to increase the storage life immensely.
In contrast, the Half Life of Polonium is 138.38 DAYS, so these "initiators"...if indeed used Polonium...would put Time as a critical factor.
No, unfortunately, the Nuke threat IS VERY REAL!!!
As to speculation about the design of the Original "Initiators", see "The Making of the Atomic Bomb" by Reeves.
The Hiroshima Weapon required NO initiator...just several Critical Masses of 90% U235...and Explosive Assembly.