If It’s More Than 90 Minutes You Aren’t Napping, You’re Sleeping As hard as it may be to leave your blissful sleep, leave the snooze button alone. Sleep expert Dr. Neil Stanley said if a nap is too long you can suffer from sleep inertia. It is a feeling of grogginess and disorientation that can last for approximately 15 minutes to two hours. Sleep expert, Alanna McGinn, said a full sleep cycles is around 90 minutes. Throughout that time you cycle through light and deep sleep. After 30 minutes your body begins to enter a deep phase of sleep. If you can, aim for 15-20
minute nap. If not, aim for 90 so that your body is entering a lighter sleep phase when you wake up. For a quick pick-me-up, 10-20 minute naps can boost energy and alertness. For all the test-crammers, a 90 minute nap boosts memory and creativity. Leave the snooze button alone.