Do not walk your young puppy for long periods, as this can result in hip and joint problems later in life.
There is a risk by all new owners of puppies to walk the young animal too far. The joints of the dog's legs remain soft and pliable for many months as the dog grows. The risk is that by over-walking the puppy on a lead, can result in the joint not forming properly, and being damaged for life.
The rule of thumb is apparently five minutes lead walk per month of life. So if the pup is 2 months old, then one would walk the pup on a lead for 10 minutes per day. It is better for the pup to be allowed to roam around and play off lead, than be forced to walk any distance on a lead.
There are numerous posts on numerous pet forums that support this. And it is better to wait and be patient, than rush the pup and have a dog with hip dysplasia or arthritis later in its life due to a rushed start.
A couple of good forum threads on the topic are