If there's VG in your mix, YES YES YES.
VG can become contaminated with bacteria, and then infect your lungs. YUCK.
PG on the other hand is antibacterial, hence why it's used in products like Ozium. So it's not as big of an issue. Which is why I never mix 100% VG.
I keep my mixes refrigerated to retain freshness.
My bottles of unflavored concentrate I also tape the cap on to minimize oxidation (darkens the liquid) and also store it IN THE FREEZER. With PG in there, it doesn't change viscosity at all.
I can tell when a bottle is spoilt after being unrefrigerated for a few days when you vape it and it has this hideous vomit flavor undertone. Not very tasty.
best thing to do is keep a few 5 or 10ml bottles to refill and carry with you, use up and then sanitize in a dishwasher before refilling. Keep your bigger bottles cold.
As far as the myths circulating attributing refrigeration as being the cause of spoilage, this defies common sense and scientific logic. My guess is either a.) a VG mix became frozen, seperated and de-emulsified and/or b.) was precontaminated and continued to spoil, even under refrigeration. Remember, people: things still continue to go bad under refrigeration or even freezing - just at a slower rate.
Of course, anything you order these days could be from fresh to years old. And unlikely to have been refrigerated continuously, if at all. And god knows how it was produced. Clean rooms are unheard of in this industry. Handwashing? Now there's a lost art. Just stand in the doorway of a public restroom sometime and observe the number of well-dressed slobs that ignore the things mommy taught them about handwashing after using the bathroom. Thinking about ejuice contamination almost makes you consider allowing FDA regulation. Or at least USDA oversight. lol.
/thinking about what that venison smelled like after being in my freezer for 3 years, yeesh!