I'm feeling grumpy so this may sound more testier than it is meant to be but... practise what and for what reason? Obviously, one practises a tremendous amount prior to ..doing something.. performing in front of people, trying out for something etc.. Then one practises an amount for ones own satisfaction and improvement - a friend who is a concertmaster in a small scandinavian orchestra does not practise 3-4 hours a day when not working on something. Obviously, if one wants to practise for 4 hours a day, one should. But a child, even an older one, should not (just my opinion) be encouraged to practise 4 hours a day on a regular basis for the sake of a theoritical career in a non-existent profession.
Just in a bad mood after a long day at my non-existent profession.