Juno was 5 months when we gave her total house/garden freedom. We stopped locking her in her crate at night at that age too. But our situation was unusual because we have a really really well behaved girl (she's 15 months now), who has always been really trustworthy. I could trust her implicitly on her own in our house or on our land and know she isn't going to wreck everything.
Our other pup, Bowser on the other hand....I don't know if I'll ever trust him. He's only 3 months old right now, but he's got the look of deviousness in his eyes.