I do understand it is to prevent joint damage......
But 16 minutes for my 16 week flatcoat retriever seems so little. I barely get out of the car and get going before it is time to turn around and go back.
I can't help thinking that the advice is simplistic. I am guessing it is to prevent silly people taking a pup on a vigorous 5 mile hike .....but when my pup gets walked its more of a gentle amble and a sensory experience than exercise. Minutes can go by as he paddles in the water, eats some horse poo and sniffs every blade of grass. In that context (a gentle walk rather than a good stride out) would it really hurt him if his walking time was extended to half an hour?