The polonium initiators generated a fizzle yield inside of one week.
Modern initiators use Dt-T reactions, and last as long as their tritium does, which is years.
The half-life of tritium is 12.3 years; however, tritium decays in to 3He2, which has a truly voracious appetite for neutrons and will generate fizzle yields in very minute quantities. A D-T initiator is going to need new tritium in less than one year.
Ye olde pin on the Holy Hand Grenade. Good call.
Question, how much apparatus and infrastructure does it take to do this kind of work? Pressure bottles, controls, flow meters... that sort of thing? How big and sophisticated does the shop have to be? Could you fit that into a container? Is there a way to stabilize the tritium for storage and transportation? Are there large power requirements?