6-8 is about the age I've noticed aspirin starts to be helpful. 60-70 degrees is really warm for pheasant hunting as far as dogs are concerned, especially if it's sunny & a dog is dark colored. Coat color makes a significant difference. They just need tons of water in those temps. If I'm going to be away from the truck more than about an hour or so in warm/hot weather like that, I try to make a point to hunt near water, so puppy can run in & cool off if needed. A brief dip in a slough rejuvenates them in a hurry, so sometimes I make him cool off a little even if he thinks he'd rather hunt. I hunt basically Saturday & Sunday each week for almost 4 months. It takes my dog maybe 4 weekends to truly get into hunting form, and by then the temps typically start to decrease pretty good. I just have no idea what it would take for him to start on day 1 of the season in peak form. Hunting is way more demanding (for my dog anyway) than any other form of exertion.