According to the guidelines of the National Sleep Foundation, the recommended time for sleeping in adults is ranged between 7 – 9 hours, whereas for some people, it can also be as low as 6 hours or as high as 10 hours. Determining what is optimal can be dependent on age, metabolic factors, physical activity, and the environmental conditions a person resides in. Finding that balance is a matter of self-discovery, where one has to experiment to get the proportions that are comfortable for the body.