"No, sitting for hours on end is not necessary. Some people think that the longer you can sit, the wiser you must be. I have seen chickens sit on their nests for days on end! Wisdom comes from being mindful in all postures. Your practice should begin as you awaken in the morning. It should continue until you fail asleep. Don't be concerned about how long you can sit. What is important is only that you keep watchful whether you are working or sitting or. . . Each person has his own natural pace. Some of you will die at age fifty, some at age sixty-five, and some at age ninety. So, too, your practice will not be all identical. Don't think or worry about this. Try to be mindful and let things take their natural course. Then your mind will become quieter and quieter in any surroundings. It will become still like a clear forest pool. Then all kinds of wonderful and rare animals will come to drink at the pool. You will see clearly the nature of all things in the world. You will see many wonderful and strange things come and go. But you will be still. Problems will arise and you will see through them immediately."
Ven. Ajahn Chah