If I may recommend something to you, as an occasional music teacher. "Every Day you forget the cello, the cello forgets you for two" - Pau "Pablo" Casals I don't know the age of your kid, but the biggest key for forward progression at any age (from 5-75) is consistency of practice, not length of time. I'd rather see my students do 15 minutes of practice every day than see them do 45 minutes every three days. Also, most of the time, you sit down for 15 minutes and it turns into 20, or 30. Often longer practice sessions for beginning and intermediate learners become a slog of "I've run out of stuff to practice, so now I have to repeat all of it all over again - and likely worse this time". If you're at upper levels, sure, practice for hours, but at a lower level that's just an exercise in futility, and an opportunity to work mistakes and bad habits into your playing. don't play it sort of right 5 times, play it right one time.