Fair enough, perhaps I was oversimplifying with my example. It seems from the OP the plan is to transition to breeding the tritium in fusion reactors, and that

Fair enough, perhaps I was oversimplifying with my example. It seems from the OP the plan is to transition to breeding the tritium in fusion reactors, and that we currently have enough fission-produced tritium to plausibly bridge to those fusion-based processes. And the concern is that the fission reactors might shut down before we bootstrap the fusion reactors. Still, as I said originally, it sounds like keeping our current level of fission reactors around should solve the bootstrapping problem.