When trying to mix new flavors or come up with a new flavor. I use PG/VG as a base with no nicotine that way if it tasts like crap i don't have to vape it. I can just throw out or try adding others flavors to it. Once I make some that i like then i can add the nicotine. Of course keeping track of what i am mixing. Saving money by not wasting all my nicotine base.