I own 6 Grouse dogs because long ago I was taught how much
ground our dogs really cover on each Grouse hunt,
over a 3 hour period, if you have a serious Grouse dog the dog will cover approx 10 miles minimum. You the hunter might walk 5-8 miles the dog 10 - 15 miles with no problem.
All this ofcourse depends on the weather and how spread out the birds are.