[neals]

No, it is never just that simple. And I don't believe anybody would say such a thing.

I can imagine being in a position where shipments can be ordered 15 days in advance, but where 45 days would be unacceptable. (train vs ship)

If that's the case, you set up your logistics to come by rail, rolling in every 15 days, instead of air and you save a bunch on your shipping.

There's so many variables and volume here, it probably makes perfect sense for a whole lot of businesses.