When to start PPC: now or once checked in?

I’ve always sold branded product but I’m launching my own now. My products was delivered today and I’m wondering when I should hit the throttle on PPC: before items are checked in and sent to fulfillment centers, once they’re en route to FCs, after they have started to be “available” at FCs, or once they’re mostly settled down at FCs?

As it stands, listing is active but if I try to order it says arrival date or 4/9 — which I assume is just a generous time frame to allow for distribution to FCs etc.

Im even wondering if I should change the start date on the listing and PPC to when the items settle down. Thoughts?