I dont do them anymore because I found it was damaging and breaking my hair off and I was left with rats in my hair. I realized what I had done when my hair grew longer. I had very thin ends. I had to trim a whole foot of thin ends off. I had grown my hair to my knees before it it wasnt that thin, I then realized it was my boyfriend who abused my hair years ago and the damage was showing as it grew out ! 
Good news is, I am no longer wih him !