IT Career Continuity

The question always arise among IT professionals, how much time should be spend in one IT job, I think the answer is not related to time, as it is related to experience attained from your IT career, I think if someday you entered your work place and at the end of work you passed out the same door, you have to ask your self one question, what did I learn at this day? If the answer in "nothing new", then it is the time to think of quiting