If you justified sleeping until 11am today by telling yourself you needed to "catch up on your sleep," well, there's some truth to your theory. The Wall Street Journal talks to sleep expert W. Christopher Winter, who says that "nobody knows how long the horizon is, probably a few nights, but studies show that recovery sleep in the short term does work." And it apparently works in both directions, with new data indicating that you can "bank sleep" by having a few long slumbers in advance of an expected rough night (Winter uses the examples of women who "bank sleep" before labor.) But there's a "but."
Banking and catching up on sleep are a distant second to Winter's No. 1 recommendation for the sleep-deprived: a nap, ideally a 25-minute one every day, at the same time. "When you schedule a short nap, your body anticipates it and slows down, without falling into a deep dream sleep." As for his emphasis on scheduling it in, "The body likes routine. When it's prepared, it works more efficiently." Click for more of his sleep observations.