We believe the best policy for this question is honesty. Tell them directly the time period you plan on staying and when you would plan on advancing your career in a different direction. If are unsure about your time period, well try to be sure before the interview! Saying you are unsure is a huge red flag. Being unsure, almost sounds dishonest. Or it signals you haven't put much thought into your career other than filling out a few job applications. So get to know your plan before walking into the interview.