I tend to marry flavors with tanks. Usually once i assign it to tank it pretty much always goes in that tank for a very long time. It makes it easy for me when i reach for something i know what i am getting else i lose track of stuff. I also tend to stick with the same few juices. Most of my vaping friends have a new juice everytime i talk to them and tend to vape that bottle dry and move to the next one. I also rebuild or replace coil and wash out tank before i would change flavors they tell me after a few puffs the flavor is gone but not in my experience.