I don't think there is an answer to this question. There are several things you should consider.
1. Did any of the answers deserve it? I have asked questions and not received a clear answer and so left it alone.
2. Are people still answering your question? I was gong to answer a question after work that was posted in the morning. When I went back a best answer was chosen within hours. In my opinion there were better answers that came after it, so I decided not to give my opinion.
3. Is the question time sensitive?