Again, like your last thread, if you mean "how long can I have a fused jumper between posts N1 and N2 on the PDC," the short answer is forever.
This is exactly how your dual AGM JL vehicle runs, as if these two posts were connected, but for an instant at cold crank and during ESS events.
There are caveats regarding this fused jumpering including limits on running ESS and how it doesn't alone solve one battery cannibalizing the other in my link.