Averages exactly the amount of time for all parts of a non-specific order to be available, the time for payments and shipping arrangements to be completed, the time for customization & final configuration if required, and varies up an indeterminate number of additional days if the shipper or weather or national holiday or other stuff gets in the way!
More seriously, the order to ship date won't be the same for all items, or even day by day. It constantly changes.
Always worth calling FRS for lead time status.
Remember that what they will tell you would be for that specific potential order, or in your case payment of an invoice, and you might want to update the shipping schedule with them at the time you actually decide to place your order or when you pay the invoice.
Thread suggestions posted on what one person experienced for their payment-to-ship date isn't really even a guide of what the delay is, even if that same person has another invoice to pay.
There is only one absolute, if you don't pay your invoice, shipment won't happen.
Again pick up the phone and call them for your situation's personalized response.
73 - David, AG4F