“Practice with your fingers and you need all day. Practice with your mind and you will do as much in 1 1/2 hours.”
Here’s a great article on how much you should practice everyday from the Bullet Proof Musician blog on How Many Hours a Day Should You Practice
This is great information about the principals of practicing to get the most out of the time you spend.
“Some of the great artists of the 20th century have shared their thoughts on these questions. I seem to recall reading an interview with Rubinstein years ago, in which he stated that nobody should have to practice more than four hours a day, explaining that if you needed to practice more than four hours a day, you probably weren’t doing it right.
Other great artists have expressed similar sentiments. Violinist Nathan Milstein is said to have once asked his teacher Leopold Auer how many hours a day he should be practicing. Auer responded by saying “Practice with your fingers and you need all day. Practice with your mind and you will do as much in 1 1/2 hours.”
Heifetz also indicated that he never believed in practicing too much, and that excessive practice is “just as bad as practicing too little!” He claimed that he practiced no more than three hours per day on average, and that he didn’t practice at all on Sundays. You know, this is not a bad idea – one of my own teachers, Donald Weilerstein, once suggested that I establish a 24-hour period of time every week where I was not allowed to pick up my instrument.”