If I had a nickel for every time I used the phrases "Work smart, Not Hard" or "Practice smart, Not hard" when my students give me the excuse that they didn't have enough time. Practice is not about punching a time card and logging the minutes or hours you spent with your instrument. Notice how I worded the end of the previous sentence? A time card doesn't reflect your "practice" time, it only reflects the time you spent with your instrument. Students often misinterpret the two and it's time to put this issue to rest.
If you ever listened to your child or yourself "practice", I have 1 question for you. Have you paid close attention to what's really going on? If the sounds you hear, are somewhat continuous, yet inconsistent, without corrections or slowing down, then you're listening to some inefficient (Not Smart) things going on. As someone who was the world's least efficient person, I know what it takes to turn it around. Making good use of your time is very important, especially when you are a professional with very limited practice time. Your goal for your practice time should be to solve a problem. If it's a particular measure, an odd shift, or several measures that give you trouble on a piece, it's important to correct the problem. You don't need to practice the stuff that sounds good, if you sound good that means the issue was resolved, Move on! How much time it takes to resolve the particular issue you have for that practice session, is on you. We are all different types of learners, which is why I don't ask for practice log cards.
If you read the article on the link below, you will find some very insightful information in this issue of practice. This subject is very important to understand, especially to the people who ask how long it takes to "get good". It depends on your definition of good. I've been playing for over twenty years and am still trying to "get good". I will say, these are all practice tips that I teach and use consistently. They have worked for me, and now researchers have evidence to solidify it. Very interesting correlation, I would say.