
I have many times taken the opportunity to have a friendly chat with puppy owners, not normally difficult as pups are people magnets anyway lol! I have spoken at length with every single person who has purchased a pup from our two litters about the dangers of over exercising. Even then, when meeting one on one occasion it was obvious they hadn't taken too much notice as our pup was put on her lead as theirs raced with their children up and down steep sand dunes! It was also very icy (beach covered in sheets of ice) so I didn't want our pup slipping! As you can imagine, I used the occasion to reiterate how important it was not to over exercise!
On the other hand, having the opportunity to meet up with puppies & their owners can help them see their where they're perhaps going wrong. One which came back for a walk with us was getting increasingly overweight, and it became obvious during our walk together that she was never let off the lead (pup was about a year old), and the poor dog was so unfit she struggled to keep up with ours! I think the owners went home with renewed vigour and knew that they had to be brave in letting her off lead for a start, also that she was too overweight (compared to my lot) and needed to lose weight! Every conversation with them after that walk centred around socialisation, exercise, and her weight.
If a breeder is lucky enough that the new owners will keep in touch (I know not all do), he/she can have ongoing influence with the raising of the pup they've bred. Of course, there are those who take the pup at 8 weeks, never get in touch again and don't follow instructions given by the breeder! I expect they're the ones who contact when the pup's 8 months to complain the dog has a joint condition!!