We are thinking of going on a long hike. About 15 km per day for a week. Weather will be mild. We have a five month old healthy pug. At the moment she appears weary after 2 hours walking with us. I wonder with two months training could she handle an extended week of hiking. I would appreciate any thoughts or experiences,
If you keep the pug fit and healthy, it could likely last on a decent hike, but 15km would be pushing it. Remember that pugs are small and don't breath well. Plus, the pug will be taking, like, 10x the amount of steps you're taking, and could have difficulty navigating rocky/uneven terrain.
If you walk it regularly and don't overfeed it, the farther your pug will be able to walk for longer. (Obesity is common in pugs.) Smaller dogs are also more easily susceptible to heat and cold, so make sure you bring lots of water, and don't hike in extreme weather.
The most important thing to keep in mind with pugs is their breathing. Unfortunately, pugs have been bred for their smooshed faces and this severely limits their breathing abilities (many pugs require manual cleaning of nasal cavities). They were not bred for their athletics, but for their looks as companion dogs to be spoiled. Their short snout also limits their panting, which is why they're not as good at regulating their temperatures as other dogs.
If you decide to take your pug out on hikes, just be aware of the temperature, terrain, and distance. Always carry water, and consider getting a pet carrier pack to hold your pug if it does get too exhausted (which is guaranteed on a 15km hike). Pugs can definitely be athletic and they love to run around, just be aware of your little guy's limitations.