I think it is dependent upon the temperature, humidity and the shape the dog is in. I rarely hunt any dog more than half-day. But I have several to choose from. I hunt in MI for grouse and hot and dry west TX for quail. My dogs can handle MI better than TX and can hunt almost daily in the Northwoods. In TX though, we usually run a brace of dogs for about 3 hours and then they get the next day off to recover. TX is hot, dry, rocky and everything has a sticker, plus I'm using big running dogs (English Pointers). There aren't very many dogs that can go "all out" with high stamina for 3 hours day after day. For example, the all-age stake at the National Quail Championship is a 3 hour race and those dogs are pretty well spent at the end of their brace and you can be guaranteed none of them were hunted 3 hours the day before the championship!
