New research has shown that "oversleeping" can be just as dangerous as a lack of sleep and it can lead to feelings of tiredness/grogginess as well. Those who sleep for more than 10 hours decrease their life expectancy. Although not dangerous on occasion if oversleeping occurs at all it can lead to days spent in a state of "sleep drunkeness" where one is neither fully awake nor asleep. This affects our ability to function and could be hazardous depending on the activities of the day. Check out the article (linked below) from CNN to find out more.