1. As long as you need. Beginners often start with short sessions: 10-20 minutes. Gradually, as one develops skill and begins receiving the benefits of meditation, the time will naturally lengthen. The length of our meditation time should be an organic, natural process of growth, not an arbitrarily enforced restriction. Eventually, one seeks to meditate whenever possible, even throughout the night. Eventually, meditating many hours a day is not only possible, but what we long for and need.
2. Time has nothing to do with meditation. We are prevented from the state of meditation by psychological obstacles. When they are removed, the state of meditation occurs. It is as simple as that. So the real question is: how long will it take for you to recognize your state of being?
“Nothing is easier than self-deceit. For what each man wishes, that he also believes.” —Demosthenes
"Do not worry; cultivate the habit of being happy." —Samael Aun Weor