It's more or less based on consistency of practice. For example, if you are practicing twice a week, it will probably take you about a year or maybe two years to start moving into what would be considered advanced beginner poses or intermediate poses. If you're doing it three times a week you will move much more quickly. The difference between doing yoga twice a week and three times a week is tremendous. The difference between three and four times a week is not as big as it is between two and three. Two and three is a big step. If you are practicing three times a week, you will notice changes very quickly, however for me there are poses that have hurt for seven years or eight years before they don't hurt anymore - it took that long for my body open up enough to do certain positions without any discomfort.
