How much yoga do you think you need to do every week? I think the answer is different for everyone based on a few variables. Age, level of fitness, injuries, how much do you use your body and for what, are you sitting in a chair all day, and so on. Having said all that, I think there are some averages on how much time to spend doing yoga and other exercises. First I will say I try to give myself some parameters, like 1 hour of strength per week, 2.5 hours of cardio type exercise, 2 full sessions of yoga per week with some additional stretching, and yoga times based on my activities. This means if I am sitting around a lot, I probably need some gentle yoga at the end of the night for about 10/15mins and conversely if I am really active the same. The idea for me is to let my body, life style and activities guide my exercise routines.
Find some routines for yourself and parameters based on your life style and needs. I will say, if I follow all the things, I feel pretty good in my body!