I do not agree to conceding a putt at any given distance when asked to do so in the main lobby. I just say....leave it up to the individual to concede at their discretion or not at all. After all, there are many holes where a 2 foot putt can be damn hard to make ( 5 and 6 Merion for example).
Conceding a putt is not a rule or a right , it is a consideration offered by an opponent and implemented at their discretion. I've played in many alts that went into extra holes where no concede is available, and have seen many games end with a 2 or 3 footer lip out ! ( Often coming off the end of my stupid worthless piece of crap putter ). ;) R