Source : Free On-Line Dictionary of Computing

burn-in period
     
        1. A factory test designed to catch systems with {marginal}
        components before they get out the door; the theory is that
        burn-in will protect customers by outwaiting the steepest part
        of the {bathtub curve} (see {infant mortality}).
     
        2. A period of indeterminate length in which a person using a
        computer is so intensely involved in his project that he
        forgets basic needs such as food, drink, sleep, etc.  Warning:
        Excessive burn-in can lead to burn-out.  See {hack mode},
        {larval stage}.
     
        [{Jargon File}]