My 6 month old girl gets tired out pretty quickly. We take her on walks to the park or to the dog park twice a day. The park is only a few blocks from our house and we play fetch with her for about 20 min until she's done. At the dog park, she'll play for an hour or so, but we can tell she's tired after like 20 min. Is this normal? Is there a general age when puppies get more stamina? I'm actually hoping she stays this way, somewhat lazy. Lol. Anybody here have a lazy gsd? She's my first, so I've got nothing to compare, but I keep reading on here that people exercise their dogs like two or three hours a day.