HOW LONG CAN A PUPPY WALK?

One of the most frequent questions I get asked during the puppy course is how far a puppy can walk. While they ask me they already give an answer, saying: "It is said that the puppy must walk 1-2 minutes per month of age!?" .... this means that a 3-month-old puppy should walk at most 3-6 minutes per day??!!