The concept of discretionary time is what you have left after sleeping, eating, and a minimum of personal hygiene:
…contrary to much of public opinion, the lifetime discretionary hours spent earning a living have declined by about one-third over the past century…In 1880 four-fifths of discretionary time was spent earning a living. Today, the lion’s share (59) percent is spent doing what we like. Moreover, it appears probable that by 2040, close to 75 percent of discretionary time will be spent doing what we like, despite a further substantial increase in discretionary time due to the continuing extension of the life span.
That is from Robert Fogel’s The Escape from Hunger and Premature Death.