If you're not a serious candidate, I think it's standard to get a ding letter pretty soon. If you haven't gotten one within a week, it's probably a good sign. A friend just got one from Heller Erhman, giving them a week ding turn around.
It also varies firm by firm. I rode the train from NYC to DC with a Fish and Richardson lawyer. He was interviewing at NYU for the day and said it'll be at least a week before their firm is procedurally able to make callback offers, maybe longer. They have to fedex forms to their Cali office. Then scan them into some computer system. Then notify the hiring committee partners. Then when all the partners approve a candidate, they can make offers.
That said, I got a 1-2 day turn around from Richard Layton Finger, Sheppard Mullin, Baker McKenzie, and McCarter English. I'm still waiting to hear from several DC firms, and Cleary in NYC.
Anyone know the turn around time for a place like Arent Fox?