The sheer size of America's incarcerated population isn't due only to sending more people to jail or prison. It is also due to keeping them there longer.
To be sure, there have been plenty of people sent. In the last twenty years, the number has shot past 2 million. It currently still stands at 2.3 - despite intense financial pressure on state budgets to reduce the bloated corrections tab.
The size of the prison population would come down significantly, though, if offenders did not stay so long. Length of stay is an important driver of the overall incarceration increase. Yet as legislators have continued to lengthen sentences and tack on enhancements, the cumulative effect has been inescapable.
As a result, length of stay is a well-established term in criminal justice discourse.
To search engines, however, the term still seems to connote length of stay in hospitals, not prisons. A simple Google search tonight for "length of stay" yielded a search results page consisting entirely of medical sources, such as this one from the Centers for Disease Control.