i'm not really sure where your coming from, CPL/IR training is broken up into different exams and licenses and ratings so i don't see how you can miss vital knowledge or experience because if you do you won't pass that particular part of the course, and the course has hour/time requirements anyway (45 hour PPL, 700 hours ATPL study etc), what is the point of slowing down your training and delaying getting to where you want to be?