I think Apple wishes that they could release a new iPhone every fall or on some kind of definite schedule. As good as they are, they're also limited by parts availability and the manufacturability of their products.
Anyway, about the shipping of their products. They've used air freight instead of boats to ship the iPad 3:
One person who contacted AppleInsider said that changes to the price of air cargo through DHL have signaled a major planned Apple shipment from China to the U.S. Evidence of this can be seen in a "big change" in shipping costs, as Apple has taken up freight capacity on flights from the Far East to America.
The massive importation of goods is said to be taking up valuable space on the courier's international flights, which has driven shipping rates up this week considerably.
The information was corroborated on Monday by MacRumors, who also spoke with sources in the shipping industry. They indicated that shipping rates rose as much as 20 percent in one week as Apple has taken up available capacity at "premium rates.
This article also talks about how Apple preships things into warehouses so they can ship to the whole country at once, which could explain the month-long window:
We've been hearing for almost two weeks now that Apple has been moving iPad 3 units into the United States, staging them through its shipping carrier's hub facilities under very high security. We can specifically say that at least one of the iPad 3 part numbers has been seen making its way into the United States. A second part number, MC744LL/A, which has so far not been linked to any specific product, has also been spotted.
It certainly appears that Apple is planning for the iPad 3 to be available very soon after its introduction on Wednesday. Consequently, the company has clearly been working hard to move massive quantities of the device into position for rapid deployment to stores around the United States and presumably a number of other countries included in the first round of launches.