Here's a quick way to figure out if a device is right for you, without a spreadsheet:

1. Count your daily puffs. If you're not sure, estimate: a typical session is 10-20 puffs, and you might have 5-10 sessions a day. That's 50-200 puffs a day.
2. Divide the stated puff count by your daily number. That gives you a rough lifespan. If a 15,000-puff device says 15 days, but your daily count is 300, you'll get closer to 50 days.
3. Check the battery capacity (mAh). Higher mAh means longer between charges. For a 15,000-puff device, you want at least 500 mAh.
4. Check the e-liquid volume (mL). More mL usually means more puffs. A 15,000-puff device should have at least 10 mL.
5. Read reviews. Search for real-world reports. If people say it dies early, trust them.

That's it. If a device's numbers don't add up, move on.