As for when they can be oredered, You can do it more or less anytime. A guy on my hall decided he wanted one a few weeks into the year, and they came and did it. It was only 20 bucks more. You'll have to clear space if you have them come in later, but that's not a big deal. If you're not sure, I'd suggest doing it that way.
Yeah, I ordered mine today, too. It's fun because you get to make jokes to your parents about your "lofty ambitions" or, the opposite, your intention to "get high" every night.