FLVPlayback ideal buffer time?

Hi, I’m wanted to know if there is any ideal value for the buffer time for a video streaming. What factors determine the video player’s buffertime so that the video plays soothly at the client end.

I’m using a buffer time of 6 sec.
My video is expected to be between 1 - 7 min. and
The player is be hosted on a public website,

which means the audience could be with varying internet bandwith. How do i know if 6 sec is perfect for my audiences or not.

Is there bright idea?