Most so-called bad batches of e-liquid are actually just a coil that needed replacing.
Nothing ruins a good flavour faster than a burnt coil. The good news is that coil life is mostly about a few simple habits.
Prime Before You Vape
Always let a new coil sit saturated with e-liquid for a few minutes before the first pull. Firing a dry coil is the fastest way to shorten its life.
Keep Your Tank Topped Up
Running low on e-liquid starves the wick, which leads straight to that burnt taste. Refill before you hit empty, not after.
Match Wattage to the Coil
Check the recommended wattage range printed on the coil and stay within it — pushing higher for bigger clouds shortens coil life significantly.
With good habits, most coils last one to two weeks of regular use before flavour starts to fade.