It is good to practice this every day or so, depending on how much of a strain you feel on your legs. You shouldn't feel much or any strain once you are out of the position, though it may be a little sore the next day. If so, take it slowly and try every two days. If you push it, you'll just end up hurting yourself.
Im 14 and i used to go martial arts 2 years ago and they forced you to do splits,i could do it although it was painful,but its been 2 years,is there a way to gain my flexibility back without pain?