While the problem with yoga is that it is devoid of myth, its redemption lies in the fact that it will accept fully any myth we bring to it. When we find the mythologies that most resonate with us, we can use them as the container to hold our unfolding practice.
While myths, as vehicles for conveying wisdom, have been around since the beginning of human history, the therapeutic use of metaphor -- the subtly structured "story with a message" -- is a more recent development.
Remember when you learned to drive a car? Didn't you need to know some basics about the car's equipment? Maybe you didn't need to know specifically how the fuel injectors interact with the fuel pump. But you at least had to understand that the gas pedal gets you moving.
What is at question, then, in the debate about short-term vs. long-term therapy is not how long the treatment takes. It is, rather, the existence, and the desirability (or not) of working with the unconscious.