I remember reading in Exploring the World of Lucid Dreaming that people practicing the MILD method with consistency and effort tend to start having lucid dreams at will (every night) after anywhere from three months to a few years. It depends entirely on the individual, as well as how much time and effort you want to spend on it.

Lucid dreams vary wildly. Some people report having ultra-realistic LD's when they first start. Many people, including myself, believe that dreams can seem more "real" than waking life in some cases. Sensations are often stronger. Others take more time to develop their dream clarity, but the general consensus on the matter is that with practice pretty much everyone can have clear lucid dreams. In a good quality lucid dream, it is essentially just like being in waking life, except that none of waking life rules apply. This is often accompanied by an intense feeling of freedom.