it really all depends on several factors mate... every terrier is different, and every handler/owner has their own expectations of what a brood worthy terriers should display before they breed.. some say 3 seasons, some 4, and some will breed the first heat (obvious wankers or peddlers).. but what if the terrier took so much stick in the first season it had to be retired due to the damage it recieved...get my point mate?? it all boils down to this question, "has my terrier shown its true worth, and am I satisfied with it's perfomance enough to breed?". because in the end mate, thats all that m