Practicing orchestral excerpts is some of the most difficult practicing we encounter as musicians. We work on long tones, flexibilities, exercise books, and solos, but these are not so physically taxing. As a result, it is important that we have an educated approach to practicing excerpts. If you  sit down and pound one after the next, you will accomplish very little. This section will outline what I have found to be the most effective way to work on excerpts.
     To begin, it is my firm belief that you should never practice excerpts for more than 45 minutes per practice session. To improve your performance of an orchestral work requires not only great endurance, it also requires mental continuity. When an individual has been working on excerpts for longer than 45 minutes, they begin to lose their focus because it is difficult to concentrate on such small details as required for this type of music. Additionally, after practicing for this amount of time, physical endurance begins to break down and the player puts his or herself in danger of short term injury. Overplaying can make you too tired to practice for another 4 hours, or it can result in a pulled muscle which can prevent you from practicing for several weeks. You do not need to push yourself that hard. If you practice for a shorter amount of time, more consistently, you rate of improvement will increase significantly.
     Consistency is the key. If you can practice excerpts every day for 15 to 30 minutes, you will improve much faster than if you practice them every other day for an hour. This is because your mental state will always be fresh. A clear mind makes for the most effective practice. For a better understanding of how to reach the optimal mental state for practicing, see The Art of Mental Practice. It is especially effective when applied to orchestral excerpts. Be as consistent as you can, down to the time of day that you practice excerpts, and you will find that your  rate of improvement and understanding of the music will increase significantly.