Man I am so lazy now. When I first started I labeled and kept track of everything. After 7 months, I don't label or keep track of a single thing anymore. Usually have six or so flavors mixed at any given time and I can tell what each one is by the way they look or what bottle I put them into, or failing that just a sniff. All my notes were so stained with juice and such a mess from revisions, I threw them out. Even my 100mg/ml base nic has been transferred to unlabeled bottles, but we have no kids, only I use them, and the nic bottles are dark blue glass so I just know what it is.
But note this works just fine for me and I'm not suggesting anyone do anything unsafe, particularly if you are new at it and have kids around.