A pretty broad question, it would depend on the maturity of the kids more so than age and where I was camped. I would easily leave my boys alone for an hour or longer in their mid teens. I’d be more wary of leaving girls alone at that age. My boys hunted with me at that age and were relatively independent. The girls were pretty level headed in the mid teens and I might leave them, but not for the same length of time as the boys. I generally tried to give the kids some slack to prove their responsibility, but not so much that anything serious could happen. The DW is more protective than me, but she recognizes it and tries to temper it.
Against the DW’s wishes, my granddaughter and a friend at 14 wanted to wander off in the forest. Boy, those genes are strong.:D I let them go but I followed at a distance. Not a lack of faith in her, but I wanted to be close enough to put an end to anything untoward that might happen. So much for stealth, she spotted me in short order. But she has an uncanny ability to spot game in heavy cover, far better than me or any other hunter I know. So we turned into a threesome wandering around the woods. Had I not followed I likely wouldn’t have let her go, though. She just didn’t have the training and experience the boys had in the boonies.