You do need practice every day no matter what level you play at but try not to think of it as how many hours each week between lessons but more of how many times you play a certain piece and how you can improve each time you play that piece. Sometimes playing a single note or phrase differently can have a great effect of the quality of your playing. You may even find yourself playing the same phrase over and over many times before it finally sounds right. This is practicing for quality and every note or pause can be looked at in this way. This is also a good way to work through your mistakes even if you have to slow down the part you are having difficulty with and working though it many times before moving on this will help you feel more confident with the difficult parts when playing through from beginning to end.  By practicing for quality in each small part you improve the overall quality of the whole piece. The more improvements you make the more you will want to practice that piece and before you know it the hour you wanted to practice will have already flown by.