Thanks Veena for the link and for your advice.
@https://www.studioveena.com/users/view/4d8119e7-5908-4e25-b252-2c3c0ac37250, I often rest until I can catch up my breath. It's like a minute or 2 until I go to the next stretch. I often change positions as I'm scared my blood doesn't flow well. If I just finish my splits 1st round for both legs, I'll go to back stretching. After a few cobra poses, I go to splits again for 2nd round. Some back bends and some headstand or elbow stand with the wall. I now will lay down flat on the yoga mat to rest for a few minutes. Then I sit to do the splits again. I feel if I sit to do splits for 10 minutes straight, it might be too long and blood doesn't flow well.
Don't know if it's right or not so right but it seems to be ok with me. Any advice is appreciated.
My whole stretching session often lasts more than 90 minutes, from warming up, stretching to cooling down.