once his back teeth were through, so probably 6/6.5 months, the chewing/biting got a lot better but he was never really a biter, more of a mouther and chewer but huge improvement once all teeth were through. We always enforced naps though and I think that made a huge difference.
I had genuinely forgotten how trying adolescence is though. We are at 7.5 months and he has the most amazing nature and I'm very grateful for that. But he is still totally over excitable outside of the house on his walks, particularly the first walk of the day and he is so strong willed. He knows exactly what you want him to do but if he doesn't want to do it, he absolutely won't do it (no matter what the treat is!). I wasn't going to do proper gun dog training with him as I felt it was a bit too regimented for his character but I'm now seriously reconsidering it!