when am i not a yoga beginner anymore??
When there is nothing left to be learned.
There’s so much to learn… were all begginers for many many years.
Just when you ‘think’ you know it all, its quite possible something will you back then you start learning again 
‘‘knock’’
Often the approach or “mind” of the student is confused with or lumped together with the basics or foundational teachings of asana (I’m assuming you are asking about asana so please correct me if I’m in error).
The approach is most profound when we, as students, are able to come to something as though it were a first time, with “beginner’s mind”, in a fresh way. This approach may not abate samskaras (etched patterns) in the consciousness but it will lessen their growth.
I sense however that you are asking “when can I move up a level in my asana practice”, “when would I be an intermediate” or “when may I begin more advanced poses”. Everyone will have a slightly different answer. Here’s mine.
When you, as a student are able to move your breath in a smooth fashion without being cued, when you understand the fundamental alignment principals, when you have a discipline to your practice, when you are able to lie still in savasana, when you can safely do standing poses, inversion, twists, and backbends, then you are no longer a beginner.
[QUOTE=YogaPrem;81960]When there is nothing left to be learned.[/QUOTE]
So true!
Being a ‘beginner’ rests upon ‘what does one begin’.
If we mean, beginning to go to a yoga studio, one is not a beginner when one spots another ‘beginner’.
If we mean, practicing asanas, one is a beginner every time one resumes after a gap.
If we mean learning what yoga really is, one is a beginner every time one realizes some truth, but something beyond still remains unknown.
If we mean enlightenment, there is no beginning and no end.
Humble people are always beginning, learning, even your teachers.
If you are speaking of asana practice I think Inner Athlete hit the mark in his reply.
What I wish to emphasize is the fact that mystical consciousness whether of a sporadic nature or a permanent feature of one’s personality is not the average or common state of human awareness. Even if the motion of thought is stilled by the practice of any discipline, the dimension of the observing consciousness is not materially affected. This is also admitted by Patanjali, author of the Yoga Sutras.~gopi k.
[QUOTE=poeticjewel95;81959]when am i not a yoga beginner anymore??[/QUOTE]
when you are not concerned about theather you are beginner or not;) really