Distance work pays off out here when we're bombing out around on the trails. Actually, even in the city, when at parks, I've had more than one occasion where I've been relieved to be able to tell my dogs to "STOP" when I see a ball hog dog racing after our ball. Most dogs who hog another's ball in my experience have been possessive of them, and it's not worth it to me to have my dogs injured in a dogfight because another person hasn't trained their dog.
I've used "STOP" when on trails and we've encounter motorcyles, ATV's, bikes, joggers, other hikers/dogs or even knowing there's cliff up ahead, being able to tell them to put on the brakes for safety reasons gives me a piece of mind.
DISTANCE work...besides STOP, SIT and DOWN have also come in handy. Distance work comes naturally when they understand stay's are part of a cue and you've done a ton of duration and distraction work when close by. Handsignals, more like arm movements, also help them out. Start off close then ping/pong the distance, next start adding distractions. I always reward in position at first so they find value in staying put.
*Remember that dogs don't have the greatest eye sight when it comes to picking something specific out in the distance. They are more perceptive to movement hence using your arm and exaggerated motion.