IMO if you know the area, and you know your dog, then its ok.
I took mine off leash since he was 6 months, its been a year now. But... im always carefull with the environment and energy, huskies are a dogs dog after all, and not matter what dogs can never be 100% trustworthy, even though i trust mine 99% of the time, that 1% could prove bad.
I live in a very urban area, lots of cars, lots of roads, lots of people and small children, but also lots of fenced fields (albeit with many opening and entrances).
oo
Atm, i take him to the back of a nearby highschool as part of our walk. But im always aware of other dogs, and children, for the most part hes good with them, but there is always that 1%. Sometime there are even a crowd of teenagers before and after school, and he runs up to them and they all love him, but for the most part the field is empty (aside from geese, and their poop:@, although ive taught him to stop eating goose poop) and he just runs and runs and every time i call him, he runs back, sits in front of me and i kiss him a thousand times lol, he loves it.
You just gotta gotta know your dog, and know the environment/situation, then plan and account for unforseen events.
Also, i dont know how you guys exercise your dogs without letting em run off leash, mine doesn't get tired, cant imagine only walking him.