Change the ff time to 10 minutes instead of 20 minutes.

From the many games I have played, I have always noticed that the ff time is 20 minutes, and by then everyone is already so tilted and pissed because of the losing game that they are forced to wait out. Why is it 20 minutes? Is it for the enemy team to have more fun demolishing the other players? Or is there an actual reason behind it? Why not make it 10 minutes so us summoners do not have to wait out 20 minutes of game time that could be spent on another, more favorable match.