Not sure as I have only been
vaping for 1.5+ months. But I must say that most all, Not All,
e-liquids I have tried smell and taste like perfume.
Still searching.
What has worked for me was blending juices to come up with something I can vape all day. Then I have some others, either straight or a blend, for occasional use.
I wouldn't doubt some of the ingredients could spoil over time depending on what they are and what they are mixed with.
Does anyone, other than the person making it, really know what is in it?