Suggestion: I'd like a "place an order for later" option.
Scenario 1: My wife's birthday is in October. She mentions something in conversation and it sparks a gift idea in my head. It's something I'm sure she won't buy for herself and something she won't get from someone else for her birthday. I go to Amazon.com and "place an order for later" specifying when I want it delivered. I give you my credit card number. A month before and two weeks before the ship date you send me reminder emails. On the calculated ship date, you charge my card and out the door the order goes. I'm the amazing husband who knew of the perfect gift and Amazon is my wing-man, Amazon's got my back, the true hero.
Scenario 2: Household or grocery items I know I'm going to need to re-stock on a regular basis (windshield wiper blades, vacuum cleaner filter - both of these are yearly replacements) can be ordered in advance so that I don't have to think about it. Amazon helps me get things done. Amazon lets me get on with life.
Upside for Amazon, you can project some future earnings, especially if people start Christmas shopping in August, which we would certainly do. Or, you only allow the option for people who have gift certificate balances in their account which means you recognize the revenue much sooner when people put a balance on their accounts.