I do 20 minutes on the whole head, which means the front 2 sections get relaxed for about 5-8 minutes and the back (which is coarse) get relaxed for longer. Since i apply my own relaxers its important that the relaxer work slow, I dont want to have overprocessed hair. I opt for mild strength and my hair straightens pretty well with Motions lye mild... but the oil version was like, well putting oil on my hair, nothing.
Mizani was the one of the strongest relaxers i've ever used, i couldn't last 4 minutes with that!