Why do flavours change after a few days?
An e-liquid is like fine wine or an old friendship: it evolves. If the flavor changes, it’s usually because your coil is starting to give up or your juice has oxidized from sitting in the sun. If it starts tasting like a burnt tire, stop looking—that’s the cotton meeting its maker.
Flavor shifts are linked to the thermal degradation of aromas and the buildup of carbonized residue on the wire (gunk). Additionally, exposure to oxygen and UV rays causes oxidation of the components, thereby altering the original aromatic profile of the blend.