Xbox Live will be down next Tuesday for 14 hours from 3AM until 5PM EST, so you shouldn't plan any marathon sessions of online gaming with your Xbox ... because you'll be a very unhappy camper. Major Nelson said this is only for internal maintenance, and there won't be any new updates to the Dashboard or anything nifty like that happening.
So prepare for an all-night session on Monday right up until the plug is pulled if you really want to get your gaming on. Fourteen hours seems like a long time for internal maintenance ... could there be something else going on behind the scenes?