Honestly? It depends on way more factors than most people realise. A decent coil should give you anywhere from 5 to 14 days of regular use, but your mileage will definitely vary. Sweet e-liquids absolutely murder coils - all that sucralose builds up and creates a gunky mess that'll have you changing coils twice as often.
Chain vaping doesn't help either. If you're constantly puffing away, you're not giving the cotton time to re-saturate properly, which leads to dry hits and premature coil death. Temperature matters too - those 80+ watt cloud builds will burn through coils faster than a 20-watt MTL setup.
Here's a tip that actually works: when you install a new coil, prime it properly. A few drops of e-liquid directly onto the cotton, let it sit for 10 minutes, then start with lower wattage for the first few puffs. It takes an extra bit of patience, but your coils will thank you for it.
Are expensive coils worth the extra money?
This is where things get interesting. Premium coils from established brands like Aspire or Vaporesso generally use better cotton, more consistent wire, and tighter quality control. You'll notice the difference in flavour accuracy and longevity - but you'll also notice it in your wallet.
Cheaper alternatives can be hit-or-miss. Some work brilliantly and offer genuine value, others are false economy that'll cost you more in the long run. The sweet spot seems to be sticking with genuine coils from reputable manufacturers, but shopping around for the best prices rather than automatically going for the most expensive option.
Which brands make the most reliable coils?
From what we've seen, SMOK coils are incredibly popular but can be inconsistent - you might get a coil that lasts two weeks or one that's done after three days. Aspire and Innokin tend to be more reliable, with better build quality and longer lifespan. Vaporesso's GTX range has been impressive lately, offering excellent flavour and decent longevity.
Geekvape coils, particularly their Z-series, have built up a solid reputation for consistency. They're not the cheapest, but they rarely disappoint. Ultimately though, the "best" coil depends entirely on your setup and vaping style.