I look at the scoring averages in the NBA. I use 12 minutes for the classic files all the way up to the 94-95 season. I use 10 minutes for the seasons beginning in 95-96 because scoring dropped a LOT during that time. But I use 11 minutes for the current 2014-15 season because the averages have risen again. But it's relative to your style of play and personal enjoyment...