Hi ! We do all do things differently, I always, once the kids were drinking a full 500ml bottle, they had 4bottles a day for weeks, then 3 bottles for 3weeks, 2bottles for 2weeks, 1bottle for a week, weaned !!! Obviously they were introduced to concentrate, hay etc from about 3weeks.
I do remember, however, when I started with goats some 27yrs ago I was told to give them milk until they were about 18months old and stud males as long as they would take it !!!! I never did and they all grew well.
More for you to filter and choose whatever is right for you and your system.