This question is often asked by those who are just starting their path in yoga. And there is no definite answer to it. This is all very individual and depends on where you want to go and how quickly.
What is your goal?
When you start doing yoga, for what purpose are you doing it? There can be many answers - to keep the body healthy, increase flexibility, improve shape. The intensity of the classes and the emphasis on certain postures, meditations, kriyas, and pranayamas depend on the goal. Whatever goal you are pursuing, I would recommend practicing every day. Even 10-15 minutes a day in the morning, afternoon, or evening will help you advance in your yoga practice.
In his book Outliers, Malcolm Gladwell cites the theory that it takes 10,000 hours of practice to become an expert at anything. Let us count. If you do yoga 12 hours a week - every week - that adds up to just 624 hours a year, which means it will take you over 16 years to become an expert in yoga. A very interesting theory that only confirms the idea that mastering skills take a lot of time and effort.
If you are just a beginner in yoga, do not be discouraged! If you devote just a little time to yoga every day, it is very beneficial for your body and mind!
And remember. You can be a master yogi and never master a yoga pose, or you can master several poses and never be a master yogi. It does not matter how flexible your body is right now, or how skillful you are at handstands or headstands. The main aspect of every yoga practice is how connected you are with your body and how calm your mind is during the practice.
Be happy!
Namaste.
