Off-leash exercise is very important to me and my guys......now that I live in the country again they get offleash hikes about 3 times per week. I can take all three myself, but I also routinely run them in a group of seven with a friend and her four dogs. One time we were up to eight dogs off-leash when she had a foster Aussie.
Now, I would be inclined to say that "it depends on the breed", however....my three are all Schnauzers - not a breed known to have excellent off-leash skills!! I am more inclined to say it depends on the DOG. Why? Because Shimmer had excellent off-leash skills from puppyhood. Zipper needed some recall teaching on a long line and focus work for about four months, and Gaci needed 4.5 years to reach that point (yeah, she's the full-on terrier...lol....found her in a few abandoned animal holes). You really need to take it dog by dog, and each dog does need individual teaching, although I have found in personal experience that working a new dog with a group of seasoned ones makes training go much quicker!!
But I think it's all dog-dependent, and dependent on how much work you are or are not willing to put into it. I feel it is important there-fore I put a lot of work into offleash responsiveness. I want a quick recall, as well as check-ins by the dogs automatically. I also use two "general" cues of "let's go" and "guys!" for different things that are not strict recalls.
There's really nothing like the joy of watching multiple dogs run offleash together, but there's also the importance of realizing the safety factor involved and knowing where/when to do it, how to teach it, and how reliable a behaviour needs to be. Safety is a huge issue, and for some people multiple dogs offleash safely is not a possibility.
Generally though I find the larger group tends to stick together more than running away, and they tended to check in with us humans more often as well! But that is just my experience, so I wouldn't want it to seem like the be-all and end-all.
A few pics (Gaci happens to not be in these, she was not out walking that day...I'll have to get some new ones with the whole gang)!

