How long would you stay to work for us if hired? What would be your answer in interview board?

They shoud not ask this question, from the CV , working history you can predict if the candidate will stay for long or he/she will stay for1 year more or less,  then move for better salary or possition if no promotion or salary incresment happen. Now is the organization choice if they nedd to hire A players or B players.

The best answer of this question is , Looking for their bright future, healthy work environment, good salary, job satisfaction, and I am pretty sure that your company give such thing so I don't need to change this company.