I remember a thread somewhere, from when Lung Juice just came out, with Drew from Nhaler saying he didn't recommend Lung Juice as an all day vape. I use Lung Juice too, but using it exclusively severely limits the flavors available. Some times I spruce it up or thin it out by mixing other juices in.
As far as speculating on the other aspects of "healthy juice", PG has good antibiotic properties, I've heard hospitals keep some amount of PG in the air (can anyone confirm this?). Sometimes I wonder if that has helped me with allergies and sinus infections which have really eased up for me since I started vaping.