Getting eight hours of shut-eye each night is generally recommended, but many people don't. As the week rolls from Monday to Friday, they accumulate a sleep debt. Spending a few extra hours in bed on a Saturday morning, people assume, will help them 'catch up' on lost sleep. They're likely right. 'Nobody knows how long the horizon is, probably a few nights, but studies show that recovery sleep in the short term does work,' says Dr. Winters, a member of the American Academy of Sleep Medicine. 'But the all-nighters I pulled in my residency 15 years ago? That's gone.'

Recent data suggests that banking sleep in advance of a long night can actually offset upcoming sleep deprivation. 'If you knew you were going to give birth on a particular day, for example, you could sleep for 10 hours a day for multiple days before the event, and be fine,' he says. Just plan ahead.

Experts refer to the effects of changing sleep habits from weekdays to weekends as 'social jet lag.' When you've revved up until midnight for five nights and then recover sleep until noon on Saturday, the body is confused. 'It's like you've traveled six time zones, and you feel terrible,' says Dr. Winters. While many sleep extenders complain of grogginess and dull headaches, subjectively they are better at performing tasks: 'I would much rather be in the passenger seat with [a driver] who's made up the sleep than someone who's simply sleep deprived.' That just-woken-up daze? It passes in a few minutes, but the benefits of extra sleep last for hours, he says.

A scheduled nap is healthier than catching up on or banking sleep. 'Because sleep extension can make you feel groggy, I always recommend a short nap, at the same time, every day,' if a person feels they need it, says Dr. Winters. He adds that 25 minutes is ideal. He tracks his alphawaves and sleep quality with a Zeo device, and sets his Sound Oasis machine to wake him after 25 minutes. 'When you schedule a short nap, your body anticipates it and slows down, without falling into a deep dream sleep,' he says. That refreshing, scheduled break is better than an occasional, disruptive weekend lie-in. 'The body likes routine,' he says. 'When it's prepared, it works more efficiently.'

There is some evidence to suggest that young people are more likely than older people to bounce back from long nights through recovery sleep, as the ability to shrug off deprivation wanes with age, says Dr. Winter. The effects of recovery may also have a lot to do with chronotype, which is genetic, and refers to whether you're a day person (lark) or night person (owl). (Most people fall somewhere in between.) 'If you're a night owl, you may do better than a morning person with an unusual schedule, so sleep-extending can be a great tool,' he says. A sleep binge is a less effective option for true morning people, who may not be able to sleep much past dawn.