superchuck:
It's a tool in your bag to use as you wish. No hard and fast rule. Go with your gut.
I second that.
The concede is a right of the player with the button and no right of his opponent. He who demands a putt to be conceded is plain wrong!
I'm strictly against any agreement as to a certain concede distance, other than 1 foot which is pointless. Firstly it depends on the green contour if a 2 or 4 foot putt is safe. Second it's a means of psychologic tactics to confuse the opponent with laxness and rigour. Especially in an A/S match, a player may become blocked out from short range putting for quite a while, then having a "simple" putt ?on an unfamiliar surface? as a stern test.
Other than that, a concede is good to accelerate the match when there's nothing to win or to lose, like in the example given.
Having said that, I frequently concede putts below 3 feet, more or less.