Hilary, it all goes by the weight and and eating habits. My bird was 4 weeks old and was weaned at 15 weeks but I still gave him some baby food till 20 weeks. You weigh the food before you give it to him and weigh it after he is done. this will tell you how much intake he is getting. Leave NOTHING TO FAITH. You're his life supply, so feedind him longer is in his best interest.
He is a baby, and even human babies eat the jar food, but sometime you need to give them a bottle.
I wish you, all the best of luck
Joe