no. it is not dangerous. but you would want to do it with the advice of a health-care professional to make sure you do it right. there are actually versions of birth control that are approved for less or even no placebo days at all -- making them continuous-use pills. if you want to change the timing of your period by adjusting when you take the placebos you should talk to your gynecologist to be sure you do it right… or you could end up pregnant.
is it dangerous to skip the sugar pills in a birth control pack to adjust a menstrual cycle?