Canine endurance is much different than humans. I would not push it any further.  Just like people, canines exercise limitations vary.  However, canines, no matter what the breed, can get heat exhaustion fairly quickly and can die from it.  Many factors such as climate, humidity, heat, time of day, age, diet all play a factor. 

I am an emergency vet tech and we treat heat exhaustion in animals frequently.  Sometimes they can recover if caught early enough but sometimes their metabolic processes begin to shut down because they can't keep up.  I would recommend running with your furry friend in shorter distances, nothing more than 5k's.  As you mentioned, providing water throughout is important.  Also canines age faster than we do.  Therefore, arthritis deveops much faster. 

Meanwhile, have fun with your dog while you can and continue to keep an eye on your canine friend.  Become familiar with normal/abnormal behavior.  They have good days and bad days too just like us.  They develop muscle strains and get cramps just like we do.  Do not hesitate to call your vet if you have any questions.