I have ran a lot with my dog for several years now (she's probably 10 now, we've ran together since about 2007, so not a young dog). It's great that you're thinking about her this way.

I like to watch how my dog recovers from running in mild/cool weather (her preference) to understand what her maximum distance really is. It's getting shorter, she used to be able to do 20 milers with me, now 12 is as far as we'll go. She sleeps it off for about a day, the day after she's not 100% but pretty close - a lot like me.

I train her like I train me - I wouldn't go out and run 20 miles tomorrow, neither should she, unless she's been doing long runs with me, too. I don't worry so much about 30 minutes of running, but anything over about 45 minutes I have to start thinking more about whether the weather is appropriate, whether she will need water, whether it's just too hot for her.

When we're running, I pay attention to whether she's just getting tired (which is okay), bored (sniffing...), or actually needs to stop (too hot, too tired, etc). How she's panting, how reluctant she is to continue, how often she wants to stop for a break. If it seems genuine, we walk for a while, or I let her rest, or give her water.

I got a RuffWear Swamp Cooler last year. It's a jacket you immerse in cool/cold/ice water and put on their back to help regulate their temperature. It did make a difference in warm weather. Sometimes we "commute" by running to work (6 miles) and it's not all in the shade. Picture of her in her jacket: https://fbcdn-sphotos-a.akamaihd.net..._6988469_n.jpg

The hard part really is knowing when they are "done" or need something, like water. I try to apply the same rules to her as I do for myself to start with.

Happy running