Its a fine line between working your dog enough to make them tired and conditioning them enough that they need ever increasing amounts of activity.
Our beagle was like that. I swear, the more we ran with her/hiked with her - the longer she wanted to run/hike! As the comment above notes - it's definitely a fine line between wearing them out and just conditioning them more!
Yep- pops used to say the exact same thing about a certain huskerboo who expected crazy exercise everyday BOL!! Its worth it though:)RA