Ray, I liked BIG running dogs not-that long ago too but the ones that "forgot to check in" weren't often enough in the ribbons. They either win or you are calling for the tracker. The wins were too few and the dog-searches were often very stressful depending on the surrounding dangers, especially when it isn't your dog.
A HOF trainer/handler once shared with me that run is an often over-rated aspect of the horseback trial and is frequently displaced with smart, strong-front-running/handling dogs that find birds and need little-to-no intervention from the handler/scout.
I had a friend who built water-dependency into his setter. It drove me CRAZY!!! Dang dog ran 15 minutes in trials then scurried back to his owner bouncing about looking to be watered!?!?! The poor dog was never in the running, no matter how many birds it handled well (usually not many if any)! Even if you aren't competing, it's a disgrace IMO.
I run early morning (rest now at this age through the late morning/afternoon) then run again in the early evening, sometimes until low light begins to compromise safety/productivity. While the summer here gets reasonably hot, the humidity can make it downright nasty!!
When I run on the prairies on a dry sunny ~ 75-85 degrees, I bring 1 bottle of drinking water. It is strictly for the one dog I'm running - not for the handler. (The handler can wait until he gets back to the truck.)
Water and the lead come out at the same time which the smart dog soon learns.
Sometimes, it's a ways back to the truck but....
It is your responsibility to
really know your dog(s) and what is safe for them to perform in. You have to recognize the indicators such as their tail, their gait, their eyes, etc.
Acclimation is HUGE. Having a dog that can run long-and-strong in Maine might last 15-20 minutes in Texas. The dog can acclimate but it takes time and patience.
To say they don't get tested in heat is ridiculous. To overdo it is irresponsible.
I witnessed a no-quit Brittany go down in a horseback trial. We poured what drinking water we had on it's head/genitals then got it to water (pond) but it had already suffered the blow. The dog had to be put down months later. The owner never forgave himself. We never saw him around again.