different breeds and strains start at different ages...I have a 1/2 redbone 1/4 amer. bulldog 1/4 pitbull that looks like a pure cur dog that I really like...not the best around but pretty good. he hunted some at a year and at 2 years is fair...
my expectation of a good dog of the type I like must show something at 6-8 months old and be hunting good at a year old and put a hog at the other end of the tracks at 18 months old...but at a year he should be finding its own hog...I also make note of all the pups that start early and only breed those...over a period of time early starters beget more early starters...inbreeding and line breeding these type of dogs will clean up the gene pool sooner than later...
i agree wat your saying but @ 18 months do you expect them to stay w/ a runner  for at least 3 to 4 hours