Unless something is “off” with your health, it’s hard to get too much sleep. But “banking” extra sleep can improve your performance.
Be sure to get some extra sleep in advance, especially if you’re heading out on a mission—where performance really matters—or about to endure a stretch of sleep deprivation. It’s unclear how much extra sleep you need to perform your best. But some evidence suggests those who sleep approximately 9–10 hours nightly for one week—before any situation involving performance or sleep deprivation—perform well. And those who bank extra sleep before a sleep-deprivation event tend to bounce back quicker during recovery time.
What about extreme sleepiness? If you’re unable to wake up or stay awake after you’ve had plenty of sleep, you might be experiencing hypersomnia. Make sure to consult your healthcare provider.