I have a lakeland dog there at 16 months,he has had 2 3 foot digs but i am holding him back till this winter,however i had 2 brothers of his from a previous litter,same dam and sire and i sold them because they wernt showing signs of starting at nearly 2 year old,my mate is now digging with these 2 dogs flat out so it just goes to show that you have to have faith in your terriers and give them the time they need