I don't think it really matters whether you bill multiple days on one form or if you split them out. It's really a personal choice. I personally prefer billing as much on one as I can so that I'm only completing the one form, but I don't like to hold billing either. Usually you don't get to pick whether you use the UB04 or the CMS1500. Usually the insurance carrier requires that you bill on the form that matches how they have you set up in their provider files.