Refrigeration = condensation = bacteria is the logic behind that argument.
Storing some VG heavy juices in the refrigerator will also cause them to thicken up.
E-liquid will spoil over time, and the process will be accelerated if it's exposed to too much light or heat. I just had to throw away 50mls of Pipe Sauce which got ruined during the recent heatwave here in the UK. We're not really geared up for extreme heat in this country (no air con), so I didn't have anywhere cool enough to store it for 3 weeks - Pipe Sauce doesn't do well in the fridge.
You'll know when juice is bad - the color, flavor and vapor production changes dramatically. It's worth pointing out that most e-liquids will darken in colour when stored for a long time, but not so much it should worry you.
JJ
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