Apple has once again shortened its waiting period for new iPad models. The company’s online U.S. store now shows a shipping time of within 24 hours for new iPad with Wi-Fi and iPad with Wi-Fi + 3G units, down from one to three days. Apple started out the month with a wait time of seven to ten days on new iPads, a figure that dropped on the 19th to three to five days, and was lowered again one week ago to one to three days. During the company’s…