Though this is written in the context of classical performers, it's very applicable to any genre
How Many Hours a Day Should You Practice? | Bulletproof Musician The Bulletproof Musician
Interesting article. I'm not sure if I agree with it all, but at least it makes me feel better with the amount of time that I do spend practicing. I thoroughly agree though with the aspects of analyzing the errors that occur while practicing and forming goals to aim for. Most of the time I set a goal based on an amount of time that I allow myself to learn a piece of music. This normally results in the feeling of pressure and stress to reach my goal within my given period of time, but I normally reach my goal and acquire a nice headache while doing so. My opinion is, do what works best for yourself regarding playing and practicing, but never be afraid to try a new method or approach.