these dogs purpose bred pursuit hare dogs I think they can be dropped in a little earlier than 18 month, don't get me wrong nowts spoiled by waiting, but a lot can and will do it well before that age, if ya spend enough time working with them plenty of exercise etc and then not much harm can be done, , you can always pull em back as KC did if they start to get over matched, I know he done this early season and fair play he has pulled the dog and held um back, in truth most dogs see plenty of sets of clean heels if they ran off proper testing slips, matching a different game to testing the dog