Is is alright to pump every 4 hrs during the day or do I need a set schedule like 7 am, 11 am, 3 pm. 7 pm, and 11 pm? Or can I just pump when I get up in the morning and than every four hours after that? I am using a medela pis backpack style pump. Also i am only pumping 4 oz each session ( 2 from each side) at this point. It takes less than 5 minutes per side to get the 2 oz, Am I getting the hindmilk if I pump for such a short period of time?