How long should I devote to yoga within one day?

I am beginning to start doing yoga at home. how long should I preform it per session? and is yoga something that is done everyday of the week?

somepeople do yoga everyday some 3-4 days a week. and its like 30-60 minutes long. they videos of it, and its on tv.
i used to do yoga everymorning on the weekdays but it make me so tired, because its so slow moving id end falling asleep, when i needed to leave lol.

once or twice a week.

if this is your main form of exercise prepare to be seriously disappointed.

How long should I devote to yoga within one day?

60 minutes, exercise, weekdays, yoga