There is no definite rule as to how long you must practice before seeing your true nature, and there is no definite rule as to how long the effects of the experience will last. If you've been practicing a long time, then the effects may last a while, in the sense that vexations won't arise and the feeling of selflessness will persist. But it is possible that the experience and its effects may last for a brief period of time, like a flash. In the analogy of the mountain, rather than the clouds parting and the sky turning clear, it would be like a bolt of lightning revealign the mountain for an instant, and then disappearing, leaving the traveler in darkness again.

Depending on one's karma and strength of practice, enlightenment experiences may be shallow or deep. What is the relationship between seeing into one's self-nature and enlightenment? The first enlightenment experience is called "seeing the self-nature, " but subsequent enlightenment experiences are not described in this way. Each successive enlightenment experience gets deeper. For this reason, the Ts'ao-tung sect describes five different levels of attainment.

Also, from the Ming dynasty onward, the Lin-chi (Jap. Rinzai) sect speaks of the "three barriers of attainment." The first barrier is equivalent to seeing into one's self-nature for the first time. The second barrier is called the "multiple barrier." At this level, you experience enlightenment over and over, gradually eliminating vexations and revealign wisdom. The experience of no-self remains longer each time.